Ammonia Emission and Outflow Activity in Young Stellar Objects

Size: px
Start display at page:

Download "Ammonia Emission and Outflow Activity in Young Stellar Objects"

Transcription

1 UNIVERSITAT DE BARCELONA Departament d Astronomia i Meteorologia Ammonia Emission and Outflow Activity in Young Stellar Objects Memòria presentada per Inmaculada Sepúlveda Cerrada per optar al grau de Doctora en Ciències Físiques Barcelona, setembre de 2001

2

3 Programa de Doctorat d Astronomia i Meteorologia Bienni Memòria presentada per Inmaculada Sepúlveda Cerrada per optar al grau de Doctora en Ciències Físiques Director de la tesi Dr. Guillem Anglada

4

5 Contents Resum de la tesi: Emissió d amoníac i ejecció dematèria als objectes estel lars joves vii Agradecimientos xxxi 1 Introduction Interstellar medium Molecular clouds Dense cores Evolutionary sequence of young stars Molecular outflows Herbig-Haro objects Interstellar ammonia: Its role in the study of dense cores Physics of the NH 3 molecule NH 3 in dense cores Main goals of this work Ammonia observations towards molecular and optical outflows 33 i

6 ii CONTENTS 2.1 Introduction Observations observations observations Results M North M South L L NGC 281 A-West HH HH L1551 NE L RNO HH HH HH 86/87/ L1641-N IRAS L1641-S CB

7 CONTENTS iii L IRAS CB L L L L L IRAS IRAS V1057 Cyg L CB IC 1396E HHL L IRAS L L NGC L Discussion

8 iv CONTENTS Location of the exciting sources of the outflows Physical parameters of the dense cores Evolutive differences in the outflow sources Conclusions Infrared images, 1.3 mm continuum and ammonia line observations of IRAS Introduction Observations Near-infrared images mm continuum emission cm continuum emission Ammonia line observations Discussion Infrared nebulosity Energy distribution Dense core Conclusions High angular resolution VLA ammonia study of L Introduction Observations Results

9 CONTENTS v Cloud structure Velocity distribution Velocity dispersion Physical parameters of the cloud Discussion Conclusions Conclusions 195

10 vi CONTENTS

11 Resum de la tesi: Emissió d amoníac i ejecció de matèria als objectes estel lars joves 1. Introducció Les estrelles es formen en els núvols moleculars interstel lars. Aquest núvols constitueixen la part mes freda i densa del medi interstel lar. El seu interior està protegit de les radiacions externes pels grans de pols, els quals permeten la formació de molècules. El component principal d aquests núvols és la molècula d hidrogen. Com que l H 2 no presenta transicions fàcilment detectables en les condicions físiques generals dels núvols moleculars, el seu estudi global es realitza mitjançant l observació d altres molècules menys abundants. La molècula de CO, que és la molècula més abundant després de la d H 2, ha sigut la més ampliament utilitzada, d entre més d un centernar de molècules detectades, per fer un estudi generalitzat dels núvols moleculars. La major part de la massa molecular de la Galàxia forma part dels anomenats núvols moleculars gegants, els quals tenen típicament una massa entre 10 5 i10 6 M, la seva grandària característica és de pc i la temperatura generalment és de K. Per tant, són els objectes més grans, més massius i més freds de la Galàxia. Els núvols moleculars més petits, amb masses < 10 4 M, sel s acostuma a denominar núvols foscos. Els núvols moleculars no són homogenis, sinó queestàn constituits per moltes condensacions més denses i més petites. Aquestes condensacions tenen formes molt vii

12 viii Resum diverses, des d una forma pràcticament esfèrica fins a una forma allargada i filamentària, i s acostumen a denominar nuclis de gas dens. La densitat característica dels núvols moleculars és de 100 molècules d H 2 per cm 3, mentre que als nuclis densos la densitat de molècules és > 10 4 cm 3. Són aquestes condensacions les que, mitjançant un procés de contracció gravitatòria, donaran lloc a la formació d objectes estel lars al seu interior. Els estudis en la molècula de CO, que traça la distribució global del gas a tot el núvol molecular, no permeten ressaltar les petites condensacions d alta densitat, sinó quesón preferibles els estudis amb molècules (anomenades traçadores del gas dens) que només emeten significativament quan la densitat supera valors de cm 3. Una de les molècules traçadores d alta densitat més ampliament utilitzades és la d amoníac. La molècula d NH 3 té unes característiques especials que la fan molt útil per a l estudi de regions de formació estel lar. Degut a la simetria de la molècula, es produeix un desdoblament per inversió dels seus nivels rotacionals. Les transicions entre aquests nivells d inversió tenen lloc fàcilment en les condicions típiques dels nuclis de gas dens i, presenten estructura hiperfina que permet obtenir amb fiabilitat diversos paramètres físics d aquestes condensacions. A més, a partir de la comparació de les transicions d inversió de diferents nivels rotacionals es pot obtenir una estimació molt bona de la temperatura cinètica del gas. Al llarg del procés que donarà lloc a la formació d una estrella es produeixen canvis en la distribució espectral de l energia que emet l objecte. Mitjançant aquesta distribució d energia es poden identificar i classificar els objectes protoestel lars en diferents etapes evolutives. D altra banda, al llarg d aquestes etapes també anirà canviant la relació i interacció entre l objecte estel lar en formació i el material (gas ipols)delseuentorn. Abans que comenci el procés de formació estel lar el que es pot observar és l emissió del gas molecular fred, mentre que a mesura que es desenvolupa l objecte central, aquest calenta el gas i la pols circumdant donant lloc a canvis en la distribució espectral d energia emesa per la font, que caracteritzen a cada etapa. Els objectes de baixa massa més joves són els anomentas objectes de Classe 0, per als quals la distribució espectral d energia s assembla a la d un cos negre fred, que correspon a la emissió de l embolcall a les primeres etapes de contracció gravitatòria. A mesura que evoluciona, el material de l embolcall es va incorporant a l objecte central (possiblement a través d un disc circumstel lar). Els objectes de Classe I encara

13 Resum de la tesi ix estan profundament immersos en el gas dens i no són detectables a longituds d ona visibles degut a que estan envoltats d una gran quantitat de pols circumstel lar. A mesura que disminueix l extinció deguda a la pols, l objecte es fa òpticament visible, encara que segueix rodejat d un disc de pols circumstel lar (precursor d un disc protoplanetari), que produeix un excés d emissió a l infraroig, constituint els anomenats objectes de Classe II (estrelles T Tauri clàssiques i estrelles de tipus FU Orionis). Els objectes més evolucionats (que ja estàn molt a prop de la seqüència principal), els quals pràcticament no tenen pols circumestel lar, i per tant no presenten excés d emissió infraroja, constitueixen la Classe III (estrelles T Tauri nues), en els quals la majoria del material original del qual s han format ja ha estat incorporat a l estrella o expulsat del seu voltant. Per a les estrelles d alta massa el procés de formació és molt més ràpid i la distinció enetapesés molt més difícil. Perquè el material del núvol es pugui acumular sobre l objecte central i aquest pugui evolucionar d una classe a una altre, es necessita un agent que permeti eliminar el material sobrant del seu voltant, així com l excés de moment angular. Hi ha diferents fenòmens observables que indiquen que els objectes joves expulsen material a grans velocitats. Els anomenats objectes Herbig-Haro (objectes HH) es coneixen des de la primera meitat del segle passat. Són nebulositats òpticament visibles excitades per xocs, amb velocitats característiques de centenars de km s 1. Més recentement, s ha observat que els objectes HH sovint s alineen formant cadenes de nebulositats, molt col limades, que anomenarem jets òptics. Si els xocs calenten el material molecular a temperatures de l ordre de K, es pot observar l emissió de la molècula d H 2, a l infraroig, constituint els anomenats jets d H 2. L emissió del material molecular ambient, que és escombrat, es pot observar directament (generalment als espectres de CO), constituïnt els anomenats fluxos moleculars. Els fluxos moleculars tenen velocitats típiques entre 10 i 30 km s 1,més petites que els jets òptics,, encara que alguns poden arribar a més de 100 km s 1. Una de les principals característiques dels fluxos moleculars és la seva bipolaritat. Generalment, consisteixen en dos lòbuls de gas, un corregut al vermell i l altre al blau, amb l objecte estel lar jove al centre de simetria. Possiblement, la bipolaritat és degudaalapresència d un disc circumstel lar al voltant de l objecte jove. Sembla ser que tots els objectes estel lars, durant el procés de formació, passen per una etapa de flux molecular bipolar. Aquests fluxos són més prominents i col limats als objectes més joves (Classe 0) mentre que desapareixen a les etapes més evolucionades (Classe II i Classe III). Generalment, tant el fluxos moleculars com els jets òptics i objectes

14 x Resum HH són fenòmens que tenen lloc a escales grans lluny de l objecte que els impulsa. Per tant, és important identificar la posició de la font excitadora, particularment quan hi ha més d un candidat. La detecció d una condensació de gas dens pot ser una eina útil per localitzar la presència de l objecte. Resulta interessant realitzar observacions del gas dens amb diferents resolucions angulars, per així estudiar tant l estructura a gran escala de les condensacions (amb observacions amb una sola antena de resolució angular relativament baixa) com l estructura a petita escala (amb observacions interferomètriques d alta resolució). Les observacions interferomètriques no són sensibles a les estructures extenses, però permeten resoldre els detalls més petits per estudiar de manera més directa la interacció del objectejoveambelmaterialquetemés a prop o separar les contribucions d altres objectes pròxims en cas de formació estel lar múltiple. Donat que les estrelles es formen a partir del gas més dens i que a les primeres etapes de la seva evolució interaccionen amb el material que les envolta (i en el cas de formació d estrelles no aïllades també amb les estrelles properes), és molt important estudiar la relació entre el gas dens i la estrella a mesura que aquesta evoluciona. Per això, en aquest treball hem realitzat un estudi sistemàtic de la distribució del gas d alta densitat, a través de l observació de l emissió delamolècula d NH 3 amb el radiotelescopi de 37 m de l observatori de Haystack, en una mostra àmplia de regions de formació estel lar, amb la finalitat d estudiar com evolucionen les propietats del gas dens. En particular, hem estudiat la relació entre les condicions físiques del gas dens al voltant de l objecte i la presència de fluxos moleculars o òptics, per tal d obtenir-ne una seqüència evolutiva. També hem utilitzat aquest tipus d observacions per identificar les fonts excitadores, tant de fluxos moleculars com d objectes HH. A més, hem realitzat estudis amb més detall de dues regions particulars. A la regió de IRAS , a més de l estudi en NH 3,hemfet un estudi a diferents longituds d ona, entre 1.2 μm i 3.6 cm, utilitzant diversos instruments. D altra banda, a la regió de L1287 hem fet un estudi de l emissió d NH 3 amb alta resolució angular utilitzant el sistema interferomètric Very Large Array (VLA), éssent aquest l estudi de més alta resolució i sensibilitat que s ha aconseguit d aquesta regió.

15 Resum de la tesi xi 2. Observacions d amoníac a regions amb fluxos moleculars i òptics Les primeres etapes de l evolució estel lar estàn dominades per processos de pèrdua de massa a velocitats supersòniques. Aquests processos es posen de manifest per la presència, en el domini ràdio, de fluxos moleculars, i en l òptic, per la presència d objectes Herbig-Haro i jets altament col limats. Els fluxos moleculars són una de les primeres manifestacions observables al començament de l evolució estel lar. Però, els objectes més joves, també poden estar associats a objectes Herbig-Haro, el que indica que no només els fluxos moleculars, sinó tambéelsòptics es produeixen a les primeres etapes del procés de formació estel lar. Una de les grans incògnites que encara no han estat resoltes respecte als fenòmens associats als objectes estel lars joves és el mecanisme impulsor dels fluxos moleculars bipolars. S han proposat models en els quals un vent estel lar d alta velocitat i molt col limat (evidenciat per la presència d objectes HH i jets òptics) impulsa el material molecular de l entorn, que es mourà amb menys velocitat i presentarà ungraude col limació menor, i que donarà lloc al que s observa com a flux molecular. En aquests models unificats, ambdós fluxos, molecular i òptic, coexisteixen durant les etapes pre-seqüència principal. Però, depenent del tipus d observacions, pot semblar que domina un tipus de flux o un altre en funció de l estat evolutiu de l objecte. Als objectes més joves, que encara estan profundament immersos en el material d alta densitat, s espera que els jets òptics siguin difícils de detectar, mentre que els fluxos moleculars serien molt més prominents. A mesura que l objecte evoluciona, el gas molecular circumdant és escombrat, i els jets es tornen més fàcilment detectables a l òptic. Per tant, seria d esperar que aquesta disminució del gas d alta densitat al voltant de l objecte produeixi una disminució de la intensitat de les línies d emissió de molècules traçadores d alta densitat, com l NH 3. Un altre punt important en l estudi dels fluxos és la identificació delafont excitadora. Aquestes fonts estàn normalment immerses en el gas dens i, per tant, hom espera que estiguin situades molt a prop del màxim d emissió dels traçadors d alta densitat, com l NH 3. D aquesta manera, les observacions d amoníac poden ser una eina molt útil per ajudar a establir la posició de la font excitadora, per confirmar una font previàment proposada com a candidata o per discriminar entre diverses candidates.

16 xii Resum Per estudiar aquests punts, hem observat l emissió de les transicions d inversió dels nivells (J, K) =(1, 1) i (J, K) =(2, 2) de la molècula d amoníac en una mostra de 53 regions de formació estel lar seleccionades amb el criteri de presentar fluxos moleculars i/o òptics. Les observacions es van realitzar amb el radiotelescopi de 37 m de l Observatori de Haystack en dos programes observacionals diferents. En el primer programa observacional, que es va realitzar al febrer de 1990, vam observar l emissió d NH 3 en 15 regions. En el segon programa observacional, realitzat al gener de 1993, maig de 1996 i desembre de 1997, vam ampliar la mostra inicial, observant l emissió d NH 3 en 38 noves regions i en algunes posicions addicionals de les regions observades en el primer programa. Vam detectar l emissió de la transició (1, 1) en 40 fonts de les 53 observades. La transició (2, 2) es va observar en 23 fonts de les quals vam detectar 16. També, vam fer observacions de l emissió màser d H 2 Oen quinze fonts i vam detectar-la en tres d elles. Les dades obtingudes han estant analitzades amb el sofware CLASS i GRAPHIC. A partir de l ajust de les components hiperfines magnètiques de l espectre d NH 3 hem obtingut els paràmetres de línia, tant per a la transició (1, 1) com per a la (2, 2), per a cadascuna de les 53 regions observades. Aquest ajust s ha fet a tots els punts observats, per tal d elaborar els mapes de l emissió de l amoníac. Per a cada una de les regions s ha cartografiat l estructura del gas dens, traçada per l emissió de l NH 3, s ha estudiat la cinemàtica, temperatura i altres paramètres físics tals com la massa o la densitat de la regió. El resum del paramètres físics que hem trobat per a cada regió delamostraespresentaalataula1.amés, hem realitzat un estudi minuciós, per a cada regió, de la relació de les nostres observacions amb els objectes associats i amb la seva distribució espectral d energia. A la Taula 3 presentem un resum de les propietats més rellevants de les fonts associades a les regions que hem cartografiat. S ha estudiat la relació entre els resultats de les nostres observacions i els obtinguts amb observacions anteriors d altre tipus. Però, molt particularment, s ha estudiat en profunditat la relació del gas dens i la presència de fluxos moleculars i/o òptics associats amb cada regió. De les 53 regions observades, hem detectat emissió denh 3 (1,1) en 40 regions. L elevada proporció de regions detectades en NH 3 indica clarament que l emissió d amoníac està relacionada amb l activitat dels fluxos. Aquest resultat confirma que els objectes són molt joves, ja que encara estan associats, i en molts casos immersos, en el gas dens del qual s han format. En tots els casos en que hem pogut fer un mapa

17 Resum de la tesi xiii Taula 1: Paràmetres físics de les regions observades Regió Dimensions a b T rot N(H 2 ) c M d e M vir n(h 2 ) f (arcmin) (pc) (K) (10 22 cm 2 ) (M fi ) (M fi ) (10 3 cm 3 ) M N (2. 0 8; ) 3:9 2:7 0:96 0: :7 6: M N (0; 0) 3:0 2:0 0:75 0:50» 15 0: ο 2.6 M S 3:7 2:4 0:91 0:59 ο 13:5 0:7 2: ο 2.8 L1287 3:8 1:9 0:93 0: :6 7: L1293 2:7 2:0 1:26 0:94» 13 1: ο 7.7 NGC 281 A-W 1:9 1:6 1:88 1:62 ο 20 1:3 6: ο 1.3 HH31 2:8 2:0 0:11 0: :7 7: HH265 4:2 2:3 0:20 0:11» 9 3:3 9 2 ο 11.3 L1551 NE 1:4 1:4 0:07 0:07 ο 25 1:0 5: ο 1.1 L1634 2:6 2:1 0:34 0:28 ο 12 1:6 2: ο 13.1 RNO 43 2:6 1:5 0:30 0:18 ο 15 ο 0:4 ο 3 10 ο 1.6 HH 83 > ο 2:5 2:3 > ο 0:34 0:31 ο > ο 5 > ο 6 > ο 1.5 HH 84 > ο 2:6 2:5 > ο 0:36 0:34 ο > ο 8 > ο 66 > ο 0.5 HH 86/87/88 2:4 1:9 0:33 0:26 ο 19 ο 0:3 ο 4 16 ο 24.0 L1641-N 2:3 4:5 0:32 0:63 ο 23 ο 3:5 ο ο 5.9 IRAS :1 1:9 1:60 0: :9 5: L1641-S3 (high velocity) 3:8 2:2 0:53 0:31 12:6 2:4 4: L1641-S3 (low velocity) 5:8 2:8 0:81 0: :7 3: CB 34 2:0 1:7 0:89 0:76» 12 1: ο 7.8 HH 270/110 (0; 0) 1:4 1:6 0:19 0:21 ο 13:6 0:7 2: ο 2.5 HH270/110 ( ; 0) 2:8 1:7 0:37 0:23 ο 13:6 0:8 1: ο 10.0 IRAS :6 1:7 1:59 1:05 ο 15:5 0:5 0: ο 14.3 HH 111 1:6 1:8 0:22 0:23 ο 13 0:5 1: ο 5.6 CB 54 1:7 1:6 0:74 0:68» 15 1: ο 3.3 L100 > ο 2:3 2:4 > ο 0:15 0:16 ο > ο 1 > ο 3 > ο 1.1 L483 2:0 1:8 0:12 0: L379 2:0 2:0 1:16 1: :4 21: L588 4:1 1:9 0:37 0:17 ο 8 4:1 11: ο 7.5 L673(NW) g 4:7 2:0 0:41 0:18» 12 2: L673(SE) h 2:2 2:0 0:19 0:17» 12 2: ο 10.9 IRAS (0; ) 3:1 2:0 0:63 0:41 16:8 3:6 9: IRAS ( ; ) 3:0 2:0 0:61 0:41 16:8 1:8 3: IRAS :7 2:0» 1:99 2: » 3200» V1057 Cyg 1:4 1:4 0:29 0:29 ο 10 0:2 6: :3 0.7 L1228 2:9 1:9 0:25 0: CB 232 2:6 2:5 0:45 0:43» 11 0: ο 2.2 IC 1396E 3:2 1:9 0:70 0: :4 3: HHL 73 ( 2:8; 7) 2:7 2:0 0:71 0: HHL 73 (8:4; 2:8) 3:1 2:4 0:81 0:63» 19 0: L1165 3:5 2:3 0:76 0:49 ο 9 0:9 7: ο 1.3 IRAS :1 2:3 0:81 0:59 ο 15:8 0:6 1: ο 4.1

18 xiv Resum Taula 2: Continuació Region Dimensions a b T rot N(H 2 ) c M d e M vir n(h 2 ) f (arcmin) (pc) (K) (10 22 cm 2 ) (Mfi) (Mfi) (10 3 cm 3 ) L1221 2:1 2:0 0:12 0: :9 7: IRAS :3 2:0 0:29 0: IRAS :0 1:8 0:61 0: NGC :5 2:4 1:96 1: :3 7: L1262 2:8 1:7 0:16 0:10» 9 4: a Dimensions del contorn a pot encia meitat de l'emissió d'nh 3. Per a les regions L1551 NE i V1057 Cyg, que no est an resoltes angularment, s'ha suposat una extensió igual a la del feix del radiotelescopi. b Temperatura rotacional, obtinguda a partir del quocient entre la densitat columnar dels nivells (1; 1) i (2; 2) d'nh 3 per a les regions on l'emissió de la l nia (2; 2) ha estat detectada. Per a les regions no detectades en la l nia (2; 2) s'ha obtingut un limit superior suposant que l'emissió és opticament prima. Per a les regions on no s'ha observat la l nia (2; 2) hem suposat que T ex (CO) = T k = T rot (22 11), les dades de CO són de Yang et al (M S), Henning et al (NGC 281 A-W), Moriarty-Schieven et al (L1551 NE), Cabrit et al (RNO 43), Bally et al (HH 83), Morgan & Bally 1991 (HH 84), Maddalena et al (HH 86/87/88), Morgan et al (L1641-N), Reipurth & Oldberg 1991 (HH 270/110 and HH 111), Snell et al (IRAS 05490), Parker et al (L100), Parker et al (L588 and L1165), Levreault 1988 (V1057 Cyg) i Dobashi et al (IRAS 22134). Per a L1634, s'ha suposat T rot =12K. c Densitat columnar d'h 2, obtinguda a partir de la densitat columnar dels nivells rotacionals (1; 1) i (2; 2), suposant que les poblacions dels estats rotacionals metastables de l'nh 3 estan en equilibri termodin amic local una temperatura T k = T R (22 11), i una abund ancia [NH 3 /H 2 ]=10 8 d Massa de la condensació, obtinguda a partir de la densitat columnar d'h 2 idel' area observada. e Massa virial obtinguda a partir de [M vir /Mfi]=210[R/pc][ V /km s 1 ] 2, on R és el radi de la condensació i V és l'amplada intr nseca de la l nia. f Densitat volum etrica, obtinguda a partir del model de dos nivells (Ho & Townes 1983). g Par ametres de la condensació nordoest. h Par ametres de la condensació sudest.

19 Resum de la tesi xv Taula 3: Resum de les propietats de les fonts rellevants associades amb les condensacions cartografiades en NH 3 Regió IRAS L bol Ref. Estat Ref. Deteció en Ref. H 2O Ref. Font Ref. (Lfi) evolutiu altres longituds d'ona m aser? amb flux? M N Yes 2 Yes ? 3 M S No 4 Yes ? 3 L Class I? a 6 NIR,smm,mm,cm 7,5,8,9 Yes 6? 15 L < Yes 11 Yes 10 NGC 281 A-W a - NIR,FIR,mm 7,13,12 Yes 14 Yes 15 HH Class I 16 NIR,FIR,smm,mm 16,17,18,19 No 11 Yes 20 L1551 NE Class 0 22 NIR,smm,mm,cm 23,18,19, Yes 22 L Class 0 92 NIR,FIR,smm,mm,cm 26,17,27,23,92 No 28 Yes 26 IRS 7 b 0:03 c 92 Class I/0 92 NIR,smm 26, Yes 26 RNO Class I 96 smm,mm,cm, 99,25,97 No 80 Yes 98 HH NIR,smm,mm,cm 101,27,25, Yes 102 L1641-N Class I 21 NIR,sm,mm,cm 30,103,21,9 Yes 105 Yes Class I 106 NIR,sm,cm 30,103,9 - -? 107 IRAS Herbig Ae/B a 128 NIR 128,116 Yes 75 Yes 15 L1641-S Class I 31 NIR,FIR,smm,mm,cm 31,32,27,30,33, Yes 34 Yes 35 CB Class I 37 NIR,smm,mm,cm 37,38,36,39 No 11 Yes 40 HH 270/ Class I 42 NIR,FIR,cm 43,42,44 No 45 Yes Class I 46 NIR,cm 46, Yes 47 IRAS Class I? a 7 NIR,FIR,cm 7,13 No 14 Yes 15 HH Class 0 48 NIR,smm,mm,cm 49,25,50,51 No 28 Yes 42 CB Class I 36 NIR,smm,mm,cm 52,37,38,53 No 54 Yes 40 L < ο NIR 109 No 54 Yes 108 L Class0/I 117 FIR,smm,mm,cm 110,111,127,112 Yes 105 Yes 81 L a smm,mm,cm 55,5 Yes 56 Yes 35 L Class I 57 mm ? 57 L ? No 28 Yes No No 93 IRAS Class 0 59 NIR,FIR,mm,cm 60,61,62,63 Yes 64 Yes d NIR,cm 60,63 - -? - IRAS < ο a NIR,smm,mm 116,5 Yes 114 Yes 115 V1057 Cyg FU Or 65 NIR,IR,FIR,cm,mm,smm 66,67,68,69 Yes 70 Yes 77 L NIR,mm,cm 118,119,104 No 28 Yes 120 CB Class I 37 NIR,mm,smm 37,36, Yes 40 IC 1396E Class 0 72 NIR,FIR,mm,smm 73,74,72 Yes 75 Yes 35 HHL Yes Yes 121 Yes < Yes 122 L Class I/FU Or 78 NIR 78,79 No 80 Yes 81,82 IRAS Class I 83 FIR Yes 83 L TTau? No 91 Yes 84 L Class I/II 125 NIR,smm,mm,cm 125,27,104 Yes 105 Yes Class I 128 cm 104 Yes 126 Yes 124 NGC 7538 IRS 1-3 b ο a - NIR,FIR,mm 85,89 Yes 86,88 Yes 87 IRS 9 b ο a - NIR,FIR,mm 85 Yes 88 Yes 87 IRS 11 b a - FIR,mm,smm 85,90 Yes 88 Yes 87 L Class I 128 mm,cm 127,104 No 28 Yes 81 a Probablement es tracta d'un objecte estel lar jove d'alta massa. b Font només detectada a l'infraroig proper. No hi ha font IRAS en aquesta posició. c Lluminositat al rang submil lim etric. d Lluminositat al rang IRAS. References:(1) Yang et al. 1990; (2) Han et al. 1998; (3) aquest treball; (4) veure Taula 3.1 d'aquest treball; (5) McCutcheon et al. 1995; (6) Fiebig 1997; (7) Carpenter et al. 1993; (8) McMuldroch etal. 1995; (9) Anglada et al. 1994; (10) Yang 1990; (11) Wouterloot et al. 1993; (12) Henning et al. 1994; (13) Carpenter, Snell & Schloerb 1990; (14) Henning et al. 1992; (15) Snell et al. 1990; (16) Gómez et al. 1997; (17) Cohen et al. 1985; (18) Padgett et al. 1999; (19) Moriarty-Schieven et al. 1994; (20) Strom et al. 1986; (21) Chen et al. 1995; (22) Devine, Reipurth & Bally 1999; (23) Hoddap & Ladd 1995; (24) Rodr guez, Anglada & Raga 1995; (25) Reipurth et al. 1993; (26) Davis et al. 1997; (27) Dent et al. 1998; (28) Felli, Palagi & Tofani 1992; (29) Cesaroni, Felli & Walmsley 1999; (30) Zavagno et al. 1997; (31) Chen & Tokunaga 1994; (32) Price, Murdock & Shivanandan 1983; (33) Morgan et al. 1990; (34) Wouterloot & Walmsley 1986; (35) Wilking et al. 1990; (36) Launhardt & Henning 1997; (37) Yun & Clemens 1995; (38) Launhardt, Ward-Thompson & Henning 1997; (39) Yun et al. 1996; (40) Yun & Clemens 1994a; (41) Moreira & Yun 1995; (42) Reipurth & Olberg 1991; (43) Garnavich et al. 1997; (44) Rodr guez et al. 1998; (45) Palla et al. 1993; (46) Reipurth, Raga & Heathcote 1996; (47) Reipurth et al. 1996; (48) Cernicharo, Neri & Reipurth 1997; (49) Gredel & Reipurth 1993; (50) Stapelfeldt & Scoville 1993; (51) Rodr guez & Reipurth 1994; (52) Yun & Clemens 1994b; (53) Moreira et al. 1997; (54) Codella et al. 1995; (55) Kelly & Macdonald 1996; (56) Codella, Felli & Natale 1996; (57) Chini et al. 1997; (58) Gregersen et al. 1997; (59) Bachiller, Fuente&Tafalla 1995; (60) Chen et al. 1997; (61) Di Francesco et al. 1998; (62) Choi, Panis & EvansII1999; (63) Anglada, Rodr guez & Torrelles 1998a; (64) Brand et al. 1994; (65) Herbig 1977; (66) Greene & Lada 1977; (67) Kenyon & Hartmann 1991; (68) Rodr guez & Hartmann 1992; (69) Weintraub, Sandell & Duncan 1991; (70) Rodr guez et al. 1987; (71) Huard et al. 1999; (72) Sugitani et al. 2000; (73) Wilking et al. 1993; (74) Saraceno et al. 1996; (75) Tofani et al. 1995; (76) Kenyon 1999; (77) Evans II et al. 1994; (78) Reipurth & Aspin 1997; (79) Tapia et al. 1997; (80) Persi, Palagi & Felli 1994; (81) Parker et al. 1991; (82) Reipurth et al. 1997; (83) Dobashi et al. 1994; (84) Umemoto et al. 1991; (85) Werner et al. 1979; (86) Genzel & Downes 1977; (87) Kameya et al. 1989; (88) Kameya et al. 1990; (89) Akabane et al. 1992; (90) Minchin & Murray 1994; (91) Claussen et al. 1996; (92) Beltrán et al. 2001; (93) Armstrong & Winnerwisser 1989; (94) Larionov et al. 1999; (95) Moorkerja et al. 1999; (96) André 1996; (97) Anglada et al. 1992; (98) Edwards & Snell 1984; (99) Zinnecker et al. 1992; (100) Rodr guez & Reipurth 1998; (101) Moneti & Reipurth 1995; (102) Bally et al. 1994; (103) Chen et al. 1993; (104) Anglada et al. 1996; (105) Xiang & Turner 1995; (106) Strom et al. 1989a; (107) Morgan et al. 1991; (108) Parker et al. 1988; (109) Reipurth & Gee 1986; (110) Ladd et al. 1991a; (111) Fuller et al. 1995; (112) Beltrán et al. 2000; (113) Odenwald & Schwartz 1993; (114) Palla et al. 1991; (115) Palla et al. 1991; (116) Yao et al. 2001; (117) Tafalla et al. 2000; (118) Magnier et al. 1999; (119) Osterloh & Beckwith 1995; (120) Haikala & Laureijs 1989; (121) Gyulbudaghian et al. 1987; (122) Dobashi et al. 1993; (123) Dobashi et al. 1992; (124) Sato et al. 1994; (125) Rosvick&Davidge 1995; (126) Toth & Kun 1997; (127) Motte & Andre 2001; (128) Parker 1991; (128) Porras et al. 2000

20 xvi Resum de l emissió d NH 3 a regions associades a fluxos moleculars, el màxim d emissió es troba situat molt a prop ( < 0.1 pc) de la posició d un possible candidat a impulsar el flux molecular. Aquest resultat confirma la identificació d aquest candidats. Només hem trobat una regió, IRAS , associada amb flux molecular en la que el màxim d emissió d NH 3 està molt allunyat ( 0.7 pc) de la font proposada com a excitadora del flux. En aquest cas, pot ser que l emissió d NH 3 estigui traçant la posició d un objecte immers molt profundament a dintre del núvol, encara no detectat, i que sigui el veritable impulsor del flux. Per a la majoria de les regions que estan associades només amb fluxos òptics, l emissió denh 3 és molt dèbil, i en molts casos no coincideix amb cap objecte conegut dintre del camp observat. Això suggereix que, probablement, cap dels objectes propers que s han detectat fins al moment està relacionat amb els fluxos. Només hi ha un cas on la font proposada per excitar l objecte HH coincideix amb el màxim d emissió d amoníac i un altre cas, on l emissió és molt intensa, però nohi ha cap objecte conegut que estigui proposat com a font excitadora de l objecte HH. Les mides de les condensacions que hem cartografiat en NH 3 oscil len entre 0.1 pc i 1pc. Només per a tres regions, que són les més llunyanes de la nostra mostra, hem obtingut que la grandària arriba a ésser de l ordre de 2 pc (per a una d elles aquest valor pot estar sobreestimat ja que la distància és incerta). És destacable l alt grau d allargament de la condensació associada amb IRAS en L1251. Hi ha diversos objectes que s observen associats a l estructura allargada. Seria important proseguir l estudi d aquesta regió amb més resolució angular, per esbrinar si hi han indicis de fragmentació. També seria important fer estudis d alta resolució angular a les regions més compactes de la nostra mostra. En algunes regions hem pogut determinar la presència de subestructures; en particular, hi ha dues regions amb subestructures perfectament definides i possiblement lligades gravitacionalment. Les densitats columnars d H 2 que hem obtingut són relativament grans, de l ordre de cm 2. Aquestes densitats indiquen que l extinció visualés 10 mag. Els valors més grans de la densitat columnar, cm 2, que representen una extinció visual d unes 100 mag, els hem obtingut per a les regions L483 i L379. Aquests resultats indiquen que aquestes fonts estan profundament immerses en el gas dens. Les masses que hem obtingut per a les condensacions varien, en general, d 1 fins a 100 M, encara que també hem observat regions massives amb masses que superen les M. Els valors obtinguts coincideixen, en general, amb la massa del virial

21 Resum de la tesi xvii dintre d un factor 3, indicant que totes es troben molt a prop de l equilibri virial i que l abundància d amoníac suposada és adequada. La regió L483 és la que presenta una diferència més gran, éssent la seva massa significativament més gran que la massa del virial. Aquest fet podria indicar que aquesta font es troba encara en la fase de contracció gravitatòria i que, per tant, representa un dels objectes més joves de la mostra. Analitzant els resultats observacionals obtinguts per a la nostra mostra, resulta que hem pogut detectar 36 regions de les 43 associades amb fluxos moleculars i que, en la majoria d elles, l emissió d NH 3 és molt intensa. D altra banda, veiem que de les 10 regions observades que estan associades només amb fluxos òptics, detectem emissió només a 4 d elles i l emissió d NH 3 detectada és molt dèbil. Aquest resultat sembla indicar que l emissió d amoníac és més intensa a les regions associades amb fluxos moleculars que a les regions associades només amb fluxos òptics. Per tal de posar de manifest més clarament aquesta possible relació entre el tipus de flux i la intensitat de l emissió d amoníac, hem ampliat la nostra mostra incloent-hi els resultats d altres observacions fetes amb el mateix radiotelescopi de Haystack i obtingudes a partir de la literatura publicada. Amb aquesta mostra més amplia, hem estudiat la distribució de la intensitat de l emissió d NH 3,mesurada per la temperatura de brillantor observada (corresponent a l angle sòlid del feix principal del radiotelescopi). La temperatura de brillantor és un bon indicador de la intensitat d amoníac només per a fonts que siguin més extenses que el feix del radiotelescopi; per tant, per tal d eliminar de la mostra les fonts que no estiguin resoltes angularment, hem limitat el nostre estudi a fonts que estiguin a distàncies més a prop d 1 kpc, per a les quals suposem que l emissió detectada omple el feix. La mostra final conté 80 fonts, de les quals 31 estan associades només amb fluxos moleculars, 9 estan associades només amb fluxos òptics i 40 estan associades amb tots dos tipus de flux (vegeu Taula 4). De l estudi estadístic en aquesta mostra, hem obtingut un valor mitjà per a la temperatura de brillantor de 1.31 K (només flux molecular), 1.34 K (flux òptic i molecular) i 0.41 K (només flux òptic). Malgrat que hi ha poques fonts associades només amb flux òptic, sembla clar que a les fonts associades només amb flux òptic la temperatura de brillantor és menor que a les fonts associades amb flux molecular (o que tenen els dos tipus de flux). Per tant, es pot concloure que l emissió d amoníac és, en general, més intensa als objectes amb flux molecular que en fonts amb flux òptic.

22 xviii Resum Taula 4: Regions associades amb flux molecular i/o òptic observades en NH 3 Regió Tipus de flux Ref. b T MB N(NH 3 ) c Ref. D Ref. associat (K) (10 14 cm 2 ) (pc) M N (IRAS ) CO M S (IRAS ) CO L1287 CO L1293 CO L1448 IRS1 CO, HH 72, L1448 IRS2 CO, HH L1448 IRS3 CO, HH 4, L1448 C CO, HH 4, GL490 CO 6» 0:5» 0: L1455 IRS1 CO, HH 9, L1455 IRS2 CO, HH 9, L1489 CO, HH 10, HH 156 HH 1» 0:2» 0: HH 159 CO, HH 1» 0:4» 0: HH 158 HH 1» 0:3» 0: HH 31 CO?,HH L1524 (Haro 6-10) CO, HH 74, 14» 0:6» L1551 IRS 5 CO, HH 15, HL Tau CO, HH 17, 18» 1» L1551 NE CO, HH L1642 CO, HH 1» 0:1» 0: L1527 CO, HH 20,75, L1634 (IRAS ) CO, HH L1634 (IRS 7) CO, HH 84, RNO43(IRAS ) CO, HH 21, HH 83 CO, HH 26, HH 84 HH HH 33/40 HH 27» 0:3» 0: HH 86/87/88 HH 25» 0:2» 0: HH 34 CO, HH 30, L1641-N CO, HH 32, HH HH 27» 0:5» 0: Haro FIR CO L1641-S3(high velocity) CO HH 68 HH 1» 0:3» 0: B35 CO HH 26 IR CO, HH 36, HH 25 MMS CO, HH 76, NGC 2071 CO

23 Resum de la tesi xix Taula 4: Continuació Regió Tipus de flux Ref. b T MB N(NH 3 ) c Ref. D Ref. associat (K) (10 14 cm 2 ) (pc) HH 270 IRS HH IRAS CO HH 111 CO, HH Mon R2 CO Mon R2-N CO GGD CO RMon CO, HH 40, 35» 0:5» 0: NGC2264(HH14-4/5/6) HH 41» 1» HH 120 CO, HH 43,78, L1709 CO 1» 0:4» 0: L43 CO L100 CO L483 CO L588 CO, HH RCrA(HH 100-IR) CO, HH 1,50, RCrA(IRS 7) CO, HH 72,50, L673 CO : CB 188 CO 1» 0:2» 0: HH 32a CO, HH 17,35» 0:6» 0: L778 CO B335 CO, HH 53, L797 CO 1» 0:2» 0: IRAS CO V1057 Cyg CO L1228 CO, HH 55, V1331 Cyg CO, HH 72, L1172 CO CB 232 CO IC 1396 E CO NGC 7129 CO, HH 58, HHL73 (IRAS ) CO HHL73 (IRAS ) CO,HHL,HH 60,61, HHL73 (IRAS ) CO : L1165 CO,HH IRAS CO S140N (IRAS ) CO S140N (Star 2) CO, HH 83,

24 xx Resum Taula 4: Continuació Regió Tipus de flux Ref. b T MB N(NH 3 ) c Ref. D Ref. associat (K) (10 14 cm 2 ) (pc) L1221 CO, HH L1251 (IRAS ) CO, HH 64, L1251 (IRAS ) CO, HH 64, L1262 CO : a S'han seleccionat només regions amb dist ancia» 1kpc. b Temperatura de brillantor al feix principal del radiotelescopi a la posició onsesuposa que es troba la font excitadora. c L mit inferior de la densitat columnar promitjada en el feix a la posició on se suposa que es troba la font excitadora. Referencies: (1) Vegeu Taula 3.4; (2) Aquest treball; (3) Herbig & Jones 1983; (4) Bachiller et al. 1990; (5) Eiroa et al. 1994a; (6) Snell et al. 1984; (7) Torrelles et al. 1983; (8) Fukui et al. 1993; (9) Goldsmith et al. 1984; (10) Myers et al. 1988; (11) Benson & Myers 1989; (12) Strom et al. 1986; (13) Reipurth 1994; (14) Elias 1978; (15) Snell et al. 1980; (16) Mundt & Fried 1983; (17) Edwards & Snell 1982; (18) Mundt et al. 1988; (19) Eiroa et al. 1994a; (20) Heyer et al. 1987; (21) Edwards & Snell 1984; (22) Jones et al. 1984; (23) Anglada et al. 1989; (24) Maddalena & Morris 1987; (25) Reipurth 1989; (26) Bally et al. 1994; (27) Haro 1953; (28) Verdes-Montenegro et al. 1989; (29) Haro 1959; (30) Chernin & Masson 1995; (31) Genzel et al. 1981; (32) Fukui et al. 1986; (33) Chen et al. 1993; (34) Felli et al. 1992; (35) Herbig 1974; (36) Snell & Edwards 1982; (37) Bally 1982; (38) Loren 1981; (39) Rodr guez et al. 1982; (40) Cantó et al. 1981; (41) Adams et al. 1979; (42) Cohen & Schwartz 1987; (43) Olberg et al. 1989; (44) Persi et al. 1994(see also Chapter 2); (45) Petterson 1984; (46) Chini 1981; (47) Parker et al. 1988; (48) Reipurth & Gee 1986; (49) Ladd et al. 1991a; (50) Strom et al. 1974; (51) Marraco & Rydgren 1981; (52) Armstrong & Winnewisser 1989; (53) Frerking & Langer 1982; (54) Vrba et al. 1986; (55) Haikala & Laureijs 1989; (56) Bally et al. 1995; (57) Chavarr a-k 1981; (58) Loren 1977; (59) Ray et al. 1990; (60) Dobashi et al. 1993; (61) Gyulbudaghian et al. 1987; (62) Eiroa et al. 1993; (63) Crampton & Fisher 1974; (64) Sato & Fukui 1989; (65) Balázs et al. 1992; (66) Kun & Prusti 1993; (67) Eiroa et al. 1994b; (68) Parker et al. 1991; (69) Reipurth et al. 1998; (70) Bally et al. 1997; (71) Gómez et al. 1997; (72)Levreault 1985; (73) Hoddap & Ladd 1995;(74) Hogerheijde et al. 1998; (75) Tamura et al. (1996); (76) Gibb &Davis 1998; (77) Tafalla et al. 1997; (78) Nielsen et al. 1998; (79) Anderson et al. 1997; (80) Whittet et al. 1996; (81) Mundt & Eislöffel 1998; (82) Devine, Reipurth & Bally 1997; (83) Davis et al. 1998; (84) Davis et al. 1997;

25 Resum de la tesi xxi NOMBRE DE REGIONS Flux de CO Flux de HH & CO Flux de HH log T MB (K) NOMBRE DE REGIONS Flux de CO Flux de HH & CO Flux de HH log N (NH 3 ) (cm 2 ) Figura 1: Distribució de la temperatura de brillantor (esquerra) i la densitat columnar de molècules d H 2 cm 3 (dreta) per a fonts associades només amb flux molecular (a dalt), amb flux molecular i òptic (al mig) i només flux òptic (a baix)

26 xxii Resum Aquest resultat estadístic per a la temperatura de brillantor pot ser interpretat com indicador que les fonts amb flux molecular estan més profundament immerses en el gas d alta densitat, i envoltades de més quantitat de gas molecular (i pols), mentre que les fonts amb flux òptic, o bé han dispersat el nucli de gas dens o bé se n han desplaçat. A partir de les densitats columnars d NH 3 s obtenen resultats similars. Els valors mitjans obtinguts per a la densitat columnar de molècules d NH 3 són cm 2 (només flux molecular), cm 2 (flux òptic i molecular) i cm 2 (flux òptic). És a dir, la densitat columnar d amoníac al voltant de les fonts impulsores disminueix a mida que l activitat del flux es torna més evident a l òptic. En la Fig. 1 presentem els histogrames que mostren la distribució de la temperatura de brillantor i la densitat columnar per a les fonts amb flux molecular, ambdós fluxos i amb flux òptic solament. Aquest estudi estadístic suggereix que les fonts segueixen una seqüència evolutiva, traçada per l emissió d amoníac relacionada amb l aparença observacional del flux. Els fluxos moleculars i òptics serien fenòmens que dominarien observacionalment en diferents etapes de l inici de l evolució estel lar. En els objectes més joves, els fluxos moleculars serien més prominents, mentre que els jets òptics anirien apareixent a mesura que l objecte evolucionés. Aquest resultat no contradiu els models unificats en els quals els dos tipus de flux coexisteixen; només evoluciona amb el temps l aparença observacional del flux a mesura que l objecte va perdent el gas dens circumdant. En aquest esquema, els jets que impulsen els fluxos moleculars es farien visibles òpticament com a conseqüència de la desaparició del material circumdant, al ser arrosegat pel flux molecular. Alternativament, les diferències observades poden representar diferències intrínseques en la quantitat de gas d una regió a l altra. 3. Imatges infraroges, observacions del continu a 1.3 mm i d amoníac a IRAS En aquest capítol s estudia la regió associada a la font IRAS , a diferents logituds d ona i amb diferents instruments amb la finalitat d obtenir la distribu-

27 Resum de la tesi xxiii ció espectral d energia d aquest objecte i d estudiar el gas dens associat. D aquesta manera hem pogut conèixer millor l estat evolutiu d aquest objecte i relacionar les seves propietats amb les d altres objectes similars. Hem fet imatges a l infraroig proper, al continu a 1.3 mm i a 3.6 cm, així com observacions d NH 3. Hem estudiat la morfologia de la nebulositat infraroja que hem detectat a les imatges, així com la distribució espectral d energia des de 1.2 μm fins a 1.3 mm, a fi d obtenir els paràmetres d un possible disc circumstel lar a partir de l emissió observada a aquestes longituds d ona. També hem obtingut els paràmetres físics del gas dens en el qual l objecte IRAS està immers. Hem escollit estudiar en detall aquesta regió perquè algunes dades preliminars obtingudes a l infraroig indicaven que es tractava d una protoestrella de baixa massa que estava associat tant amb emissió òptica de l objecte Herbig-Haro HH 120, com amb emissió d unjetd H 2 molt col limat. Les imatges a l infraroig proper a les bandes J,K,H i L es van obtenir amb la Infrared Array Camera (IRAC-1) de l European Southern Observatory (ESO) instal lada en el telescopi ESO/MPI 2.2 m a La Silla (Chile). Les imatges es van processar utilitzant el software de IRAF. Les observacions de continu a 1.3 mm es van fer utilitzant el bolòmetre del Max Planck Institute für Radioastronomy (MPIfR) instal lat al telescopi submil limètric SEST de 15 m a La Silla (Chile). Les observacions del continu a 3.6 cm es van fer amb el sistema interferomètric Very Large Array (VLA) del National Radioastronomy Observatory (NRAO) en la configuració D. Les dades van ser calibrades utilitzant el paquet de software AIPS (Astronomical Image Processing System) i es van obtenir els mapes de l emissió. Les observacions d amoníac es van realitzar amb el radioteslescopi del Haystack Observatory del Northeast Radio Observatory Corporation (NROC). Es van observar les transicions d inversió (J, K) =(1, 1) i (2, 2) de la molècula d amoníac amb una resolució angular de L analisi de les dades es va realitzar mitjançant el sofware CLASS (Continuum and Line Analysis Single-Dish Software) i GRAPHIC desenvolupats per l Institut de Radio Astronomie Millimétrique (IRAM). Les imatges infrarojes indiquen clarament la presència d una nebulositat al voltant de la font IRAS. Nebulositats similars s han trobat en altres fonts IRAS candidates a protoestrelles de baixa massa. Combinant les dades de les nostres observacions

28 xxiv Resum a l infraroig proper, les dades a l infraroig llunyà obtingudes del catalèg de fonts IRAS, les nostres observacions mil limètriques i les dades submil limètriques obtingudes i publicades per altres autors, hem obtingut la distribució espectral d energia de la font IRAS Integrant aquesta distribució espectral hem obtingut una lluminositat bolomètrica de 19 M. Nomès una petita fracció ( 3%) de la lluminositat total és emessa a l infraroig proper, mentre que la major part és emesa a longituds d ona més llargues, indicant que es tracta d un objecte molt jove. L índex espectral entre 2.2 i 25 μm que hem obtingut ens indica que la font és una possible candidata a protoestrella. La intensa emissió mil limètrica detectada i la forma de la distribució d energia espectral de la font suggereix la presència d un disc circumstel lar al voltant de la font IRAS Els objectes joves que presenten una emissió en el rang de longituds d ona mil limètric i submil limètric molt més intensa que les de Classe I, formen el grup dels objectes més joves, anomenat Classe 0. L emissió delesfontsdeclasse0és més intensa perquè estan envoltades d una estructura circumstel lar molt més massiva. Un criteri proposat per classificar les fonts és en termes del quocient entre la lluminositat bolomètrica de la font i la lluminositat a 1.3 mm. El quocient de lluminositats que hem obtingut per aquesta font és similar al trobat per a les fonts extremadament joves de Classe 0 i molt més petit que el d una font típica de Classe I. La temperatura de la pols és un altre criteri proposat per distingir les dues classes; per a la font IRAS hem trobat una temperatura de la pols molt semblant a la de les fonts de Classe 0. Per tant, basant-nos en tots aquests resultats proposem que la font IRAS és una font molt jove, similar a les de Classe 0. El fet que estigui associada a objectes HH i a emissió d H 2 indica que el fenòmen dels jets òptics i d H 2 comença a les primeres etapes de l evolució protoestel lar. Les observacions d amoníac són una eina excel lent per estudiar els nuclis de gas dens. El nostre mapa de l emissió d NH 3 mostra una condensació que no està resolta pel feix del radiotelescopi (1. 4),centradaalaposició de IRAS A partir de l ajust de les cinc components hiperfines de l espectre d NH 3 (1,1) en la posició del màxim d emissió, hem obtingut els parametres físics de la condensació, que estan resumits a la Taula 5. En conclusió, les nostres observacions indiquen que la font IRAS és un objecte molt jove immers en un nucli de gas dens, envoltat d un disc circumstel lar i d un embolcall extens. Les seves característiques són molt semblants a les de les

29 Resum de la tesi xxv Taula 5: Paràmetres físics obtinguts de les observacions de NH 3 V LSR (1; 1) a 6:15 ± 0:02 km s 1 V 1=2 (1; 1) b 0:76 ± 0:05 km s 1 fi m (1; 1) c 1:1 ± 0:4 f T ex fi m (1; 1) d 3:1 ± 0:3 K f N(1; 1) e 6: cm 2 f N(2; 2) f < ο 6: cm 2 T rot g < ο 15 K f N(H 2 ) h ο 1: cm 2 A V i ο 18 mag Dist ancia j 400 pc Grand aria k < ο 0.16 pc Massa l ο 6 Mfi Massa Virial m < ο 10 Mfi n(h 2 ) n > ο cm 3 a Velocitat radial de la l nia (1; 1) respecte al sistema de refer encia local. b Amplada intr nseca de la l nia, tenint en compte la profunditat optica i les components hiperfines magn etiques de la l nia (1; 1), per o no la resolució espectral de l'espectr ometre. c Profunditat optica de la component principal de la l nia (1; 1), calculada com a la suma de les profunditats optiques de les seves components hiperfines magn etiques. d Obtingut a partir de l'equació del transport, suposant Tex fl T fons = 2:7 K,on f és el factor d'emplenat del feix del radiotelescopi, i T ex és la temperatura d'excitació. e Densitat columnar promitjada en el feix per al nivell (1; 1), obtinguda suposant Tex fl T fons. f L mit superior a 3-ff per a la densitat columnar promitjada en el feix pel nivell (2; 2). g L mit superior per a la temperatura rotacional, calculada a partir del quocient de les densitats columnars en els nivells (1; 1) i (2; 2). h Densitat columnar d'h2 promitjada en el feix, obtinguda suposant que les poblacions dels estats rotacionals metastables de l'nh 3 estan en equilibri termidin amic local a una mateixa T rot = T k = 11 K (obtinguda de les dades de CO de Torrelles et al. 1983), i prenent comavalor de l'abund ancia relativa X(NH 3 )=10 8 (Herbst & Klemperer 1973). i Extinció visual, obtinguda a partir de [AV =mag] = 10 [N (H 2 )=10 22 cm 2 ](Dickman 1978). j Pettersson 1984 k Com que la font no est a resolta, donem com a l mit superior la grand aria del feix. l Obtinguda a partir de la densitat columnar promitjada al feix i la grand aria del feix. Fem notar, que encara que la font no est a resolta, aquesta estimació és independent de la grand aria de la font. m Obtingut a partir de [Mvir =Mfi] =210[R=pc][ V 1=2=km s 1 ] 2,onR és el radi de la font. n L mit inferior per a la densitat volum etrica d'h2, estimada a partir del model de dos nivells (Ho &Townes 1983), adoptant T k =11Kif =1. Aquesta estimació és independent de l'abund ancia d'nh 3.

30 xxvi Resum fonts de Classe 0. Com que aquest objecte també és la font impulsora de l objecte HH 120, els nostres resultats indiquen que els fluxos d objectes HH es produeixen molt aviat, en les primeres etapes d evolució protoestellar. 4. Estudi d alta resolució angular amb el VLA de l emissió d amoníac a L1287 En aquest capítol fem un estudi d alta resolució angular ( 4 ) de l emissió d amoníac a la regió L1287. Aquesta regió és un núvol molecular que conté un flux molecular bipolar molt energètic. Aproximadament al centre del flux molecular s han trobat diversos objectes estel lars joves separats entre si uns pocs segons d arc. D entre ells hi ha dos, un objecte del tipus FU Orionis anomenat RNO 1C i una font centimétrica de radiocontinu anomenada VLA 3, que s han proposat com possibles fonts excitadores del flux molecular. Però, degut a la petita separació angular entre tots aquests objectes, i ja que són objectes molt joves, fins ara ha estat impossible determinar quin d ells és la font excitadora del flux molecular. Les observacions d amoníac d alta resolució són molt útils per establir la relació d un objecte amb el gas molecular, i com les fonts excitadores dels fluxos moleculars es troben associades amb gas molecular, les nostres observacions poden ser molt útils per clarificar la relació de cada un d aquests objectes amb el flux molecular. L estudi d alta resolució angular que hem realitzat de l emissió d NH 3 en aquesta regió ens ha permés estudiar la distribució del gas d alta densitat des d escales angulars de 3 fins a 2,així com estudiar la cinemàtica, la distribució dedensitat columnar i de temperatura a l estructura del gas dens a una escala de 5000AU, per tal de determinar la relació d aquests paràmetres amb les propietats dels diferents objectes estel lars joves que s han trobat associats amb el centre de l estructura de gas dens. Les nostres observacions són les més sensibles i de més gran resolució angular de les que s han realitzat fins ara del gas molecular a aquesta regió. Les observacions es van realitzar amb el sistema interferomètric Very Large Array (VLA) del National Radioastronomy Observatory (NRAO) en la configuració Del 31 d agost de Vam observar simultàniament les transicions d inversió (J, K) = (1, 1) i (2, 2) de la molècula d amoníac. Les dades van ser calibrades i analitzades amb el paquet de software AIPS (Astronomical Image Processing System) i vam

31 Resum de la tesi xxvii obtenir els mapes de l emissió d NH 3 i de la distribució develocitats. L emissió d NH 3 que hem cartografiat (a partir de les nostres observacions integrant l emission per a tots els canals de velocitat) traça una condensació de gas dens de 35 pc allargada perpendicularment a l eix del flux molecular. Tots els objectes estel lars joves es troben molt a prop del centre de d aquesta estructura. La temperatura promig que hem trobat per a aquesta condensació de gas dens és de 17 K, el que indica que els objectes que estan immersos en ella produeixen un calentament significatiu del gas molecular. La massa total obtinguda és de 55 M,queés molt més gran que la que havien obtingut altres autors amb observacions interferomètriques de més baixa sensibilidad amb les quals només van poder cartografiar la part més central de la condensació. Per tant, les nostres dades ofereixen la millor imatge d aquesta condensació de gas dens a una escala angular des de 80 fins a 4. Tota la condensació presenta una cinemàtica molt rica i complexa. Hem trobat un gradient de velocitat al llarg de l eix principal de la condensació que suggereix que tota la condensació pot estar en rotació. La velocitat de rotació aparentment disminueix amb la distància al centre, a escales de 25 AU fins a 0.2 pc. La posició de les fonts RNO 1C i VLA 3, així com la d altres dos objectes (VLA 1iRNO1B)està molt a prop de dos màxims locals d emissió d NH 3. Al voltant d aquests objectes la densitat columnar és de cm 2 i la temperatura d uns 20 K. Altres dos objectes (VLA 2 i VLA 4) estan situats en una regió onladensitat és més baixa ( cm 2 )però la temperatura és molt més elevada (25-30 K). També hem trobat un tercer màxim (separat uns 15 d els altres dos), que no està associat a cap font. Les nostres dades suggereixen que aquest màxim podria estar traçant la posició d un objecte, encara no detectat, molt jove i molt profundament immers en el gas dens. La morfologia que presenta la condensació en els diferents canals de velocitat suggereix que el centre de la condensació conté una cavidad creada pel flux molecular amb els objectes VLA 2 i VLA 4 situats en les parets interiors de la mateixa. Un dels motius que afavoreixen la font VLA 3 com el millor candidat per impulsar el flux molecular, és que presenta un allargament en la direcció del flux molecular, que es suposa que és un radio jet que està traçant l origen del flux. El fet que nosaltres hagim detectat un valor significativament elevat de la densitat columnar

32 xxviii Resum al voltant d aquest objecte confirma que VLA 3 és un bon candidat a ser la font excitadora del flux molecular. No obstant, els altres objectes situtats al centre de la condensació també estan aparentement associats amb un gran quantitat de gas dens, éssent també bons cadidats a font excitadora. Per tant, no es pot excloure la possibilitat de que n hi hagi més d un objecte associat amb el flux molecular i que aquest, sigui de fet, la superposició de diversos fluxos moleculars associats als diferents objectes joves que hi ha a la regió. 5. Conclusions En aquest treball hem realitzat un estudi de l emissió d amoníac en una mostra àmplia de regions de formació estel lar, caracteritzades per tenir objectes joves associats a fluxos supersònics de gas molecular o bé a fluxos òptics (tals com jets o objectes HH). A més, hem realitzat un estudi intensiu de dues regions en particular. Alaregió IRAS hem estudiat la font a diferents longituds d ona i amb diferents instruments, a més d observar l emissió d amoníac amb baixa resolució angular, per tal d obtenir la distribució espectral d energia de la font i caracteritzar millor la relació entre l objecte i el gas dens. A la regió L1287, on hi ha un flux molecular i diversos objectes joves associats, hem realitzat a més de l estudi d NH 3 de baixa resolució angular, un estudi de molt més alta resolució, per establir millor l estructura a petita escala del gas dens i la relació dels diferents objectes que s hi troben associats. Com a resultat de l estudi global de l àmplia mostra de regions observades, concluim que, en general, a la major part de les fonts associades amb fluxos moleculars l emissiò d NH 3 és molt intensa i el màxim d emissió d NH 3 es troba molt a prop de la posició d un possible candidat a font excitadora. En algunes regions per a les quals no hi ha cap canditat a ser la font excitadora, el màxim d emissió d NH 3 podria indicar la presència d un objecte, encara no detectat, molt jove i molt immers en el gas dens i que seria l impulsor del flux. En canvi, a les regions associades amb fluxos òptics l emissió d NH 3 és molt dèbil i en general, el millor candidat per ser la font excitadora del flux es troba desplaçat de la posició delmàxim d emissiò. Les condensacions observades en NH 3, en general, són molt fredes, tenen amplades de línia que indiquen que la cinemàtica del núvols està dominada per moviments no tèrmics, i es troben molt a prop de l equilibri virial. Hem trobat una clara

33 Resum de la tesi xxix correlació entre l amplada de les línies d NH 3 i la lluminositat de l objecte associat, de manera que els objectes més lluminosos tenen les linies d NH 3 més amples (L bol =10 2.0±0.1 ΔV 4.7±0.4 nt ). Hem trobat evidències de fragmentació delnúvol i indicis de contracció gravitatòria algún cas. El resultat més important és el descobriment d una correlació entre la intensitat de l emissió d NH 3 ilapresència de fluxos òptics o moleculars. La temperatura de brillantor i la densitat columnar d NH 3 disminueixen a mida que l activitat del flux es torna més evident en l òptic. Aquest resultat suggereix un esquema evolutiu en el qual els objectes estel lars joves anirien perdent progressivament el gas dens que els envolta i anirien fent-se més prominents els jets òptics com a conseqüència de l efecte dels propis fluxos moleculars. Com a resultat de l estudi a la font IRAS , hem conclòs que aquest és un objecte molt jove profundament immers al gas dens i que està envoltat d un disc circumstel lar id un granembolcall de pols. Lescaracterístiques d aquest objecte són semblants a les fonts de Classe 0, éssent, per tant, IRAS el prototipus d una font molt jove que impulsa tant un objecte HH com un flux molecular. Això ens indica que els fluxos òptics ja es produeixen a les primeres etapes de l evolució protoestel lar. Finalment, per a la regió L1287, el nostre estudi d alta resolució angular revela que tots els objectes estel lars jovesconegutsenlaregió estan probablement associats amb gas molecular d alta densitat. Encara que la font VLA 3 està associada amb una gran quantitat de gas dens, éssent per tant, un bon candidat a font excitadora del flux molecular, les altres fonts també són bons candidats. Per tant, és possible que el flux molecular que es veu a gran escala sigui la superposició de diferents fluxos moleculars associats als diferents objectes que es troben al centre de la condensació. La cinemàtica de la condensació és molt complexa, però lapresència d un gradient de velocitat al llarg de l eix principal de la condensació suggereix que hi ha un moviment de rotació amb la velocitat de rotació augmentant cap al centre de la condensació.

34 xxx Resum

35 Agradecimientos Por fin, aqui esta la tesis. Después de tanto tiempo, dias, tardes y noches de trabajo, al final la he acabado. Durante todo este tiempo, ha habido muchas personas que me han ayudado, de una u otra manera, a realizar este proyecto. A ellos quiero expresar mi agradecimiento. Al Dr. Guillem Anglada, director de este trabajo, quiero agradecerle todas las horas y todo el esfuerzo que me ha dedicado. Gracias por el apoyo y por todo lo quemehaenseñado, sin su ayuda nunca podria haber realizado este trabajo. Al Dr. Robert Estalella, que me siempre ha confiado en mi. Su consejo y ayuda han sido muy importantes. Al Dr. Josep Miquel Girart por su ayuda, sobre todo en la última parte de la realización este trabajo. A la Dra. Rosario López y a la Dra. Francesca Figueras por apoyarme. A los miembros del Haystack Observatory por su hospitalidad, especialmente al Dr. Aubrey Haschick, que me ayudó en la primera estancia en el observatorio. A los miembros del Departament d Astronomia i Meteorologia, todo este tiempo con vosotros ha estado lleno de experiencias muy reveladoras. Especialmente, quiero agradecer a José Ramón Rodríguez, que se haya encargado siempre de todo el papeleo, que no ha sido poco. Quiero recordar a los que han sido compañeros de despacho y pasillo, con los que he compartido buenos y malos momentos: Josefa López, Maite Beltrán, Eva Villuendas, Marc RibóyDavidLario. A mi familia, mis padres y mi hermana Marta que siempre han estado a mi lado. Gracias por vuestra ayuda y paciencia. xxxi

36 xxxii Agradecimientos Y especialmente, a Òscar Morata, la persona que mejor sabe y comprende que es lo que ha sido todo este tiempo. Trabajar a su lado ha sido una experiencia muy positiva....y a Jordi. A todos los que no nombro, pero que han sido muy importantes. Gracias a todos. Barcelona, 11 de septiembre de 2001

37 Chapter 1 Introduction The star formation process has remained a mystery for a long time. Despite centuries of astronomical observations of stars, the process of star formation has never been directly observed, even with the most powerful optical telescopes. Fortunately, in the last decades advances in observational technology opened the infrared, radio and millimeter-wave windows to astronomical investigation and enabled direct observations of star forming regions. This has expanded considerably our knowledge about the star formation process itself and about the sites where this process takes place. Now, it is well known that stars begin their lives deeply embedded in the densest cores in molecular clouds. This process of star formation is accompanied by phenomena that can be observed at radio and infrared wavelenghts. These observations have revealed that these phenomena modify entirely the medium where the stars are born. Therefore, to acquire a good knowledge about the star formation process, it is necessary to study both the physical conditions of prenatal material, (that means study the distribution and properties of dense gas within molecular clouds from which stars are formed) and the products of star formation. This study not only helps to determine the conditions and mechanisms necessary to form stars, but also provides information about the relationship between young stars and their surrounding environment. 1

38 2 Chapter 1. Introduction 1.1 Interstellar medium The interstellar medium plays a crucial role in Astrophysics because of its central importance in star formation and evolution, and in the formation and evolution of galaxies. The interstellar medium is quite complex, with atomic, molecular, and ionized gas components, dust grains, cosmic rays, magnetic fields, and radiation, all interacting through a variety of physical and chemical processes. There exists a complex interaction between stars and the interstellar medium, by the injection of energy and by the interchange of mass. Stars form from the matter of the interstellar medium and return most of their mass back to it as the star evolves. Much of the energy of the interstellar medium comes from stars, which are continually forming and dying, in the form of radiation, winds, and supernova explosions. The interstellar medium is mainly constituted by hidrogen; it is distributed over the whole Galaxy. About 10% of the atoms are helium, and a further 0.1% of the atoms are carbon, or nitrogen or oxygen. Other elements are even less abundant. Mixed with the gas are the dust grains. The interstellar medium consists of three phases: the cold medium, dense and neutral, containing both atomic (H I) and molecular (H 2 ) hidrogen at T = K; the warm medium, at T 8000 K, containig both neutral and highly ionized H I, either surrounding the cold clouds in an envelope or pervading much of the space as an intercloud gas; and the third one, the hot ionized medium, at T 10 6 K. These three phases are supossed to exist in rough pressure equilibrium. From observations of the 21 cm line of H I, a complete mapping of the structure and distribution of the atomic gas in our Galaxy have been carried out. About 50% of the mass of the interstellar medium is concentrated in molecular clouds, that occupy a small fraction of the volume, whereas much of the volume is filled with the warmer intercloud gas. These clouds are self-gravitating and have an internal pressure due to supersonic internal motions. Interstellar molecular clouds is the coldest and densest components of the intestellar medium. The interior of these clouds are partially protected from starlight by extinction because the dust grains they contain. Therefore, the conditions inside them allow the formation of molecules. The majoritary component of molecular clouds is the molecular hidrogen (H 2 ), about 36% is He and the rest is dust, other molecules and atoms. Up to now, more than one hundred of different molecular species are known to exist in these molecu-

39 1.1. Interstellar medium 3 lar clouds, from simple diatomic molecules to the more complex organic molecules. Unfortunately, observations of the molecular component of the interstellar medium are more difficult than for the atomic component. Since molecular hydrogen has a small moment of inertia and no permanent dipole moment, radio or infrared transitions are not permitted and then, direct observations of H 2 becomes impossible in the standard conditions of these clouds. However, it is possible to study the overall molecular component through observations of other molecules. In fact, our most complete image of the molecular component of the Galaxy comes from large surveys in the J=1 0 rotational line of CO, that has become an useful tracer for the H 2 gas Molecular clouds The star formation takes place in molecular clouds, so they provide the initial conditions for the process of star formation. The vast majority of known molecular clouds are currently forming stars, as evidenced by H II regions, infrared sources, heated dust, and outflows. The capability of a molecular cloud to form stars depends on its initial physical conditions, which are subject to the influence of the external medium (nearby massive stars, ionization fronts, density waves, etc.). Consequently, the knowledge of the physical conditions in the clouds and those of the immediate regions around the newly born stars are necessary steps to study and to infer the physical processes that occur during their formation. Molecular clouds are generally divided into Dark Clouds complexes which form exclusively low-mass stars and Giant Molecular Clouds which form both high-mass and low-mass stars. The physical conditions of clouds forming solely low-mass stars are quite different from those of clouds that form massive stars or both. The study of molecular clouds can be carried out through the measurement of line emission radiated by their molecular components, e.g., through CO emission (e.g. Blitz & Thaddeus 1980; Gatley et al. 1979) and by the infrared continuum emission of their dust grains. Table 1.1 summarizes the physical properties of both clouds. In general, Giant Molecular Clouds are larger, warmer, more massives and have larger line widths than Dark Cloud complexes. The width of a spectral line contains information about the velocity dispersion and hence it is a valuable probe of the motions of the gas inside the clouds. Ob-

40 4 Chapter 1. Introduction Table 1.1: Physical properties of Giant Molecular Clouds and Dark Cloud a Giant Molecular Clouds Dark Clouds Complexes Mass (M ) Size (pc) Density (cm 3 ) Line width (km s 1 ) Temperature (K) a Adapted from Cernicharo (1991) and Mundy (1994) servations of 12 CO and 13 CO in molecular clouds have revealed that the line widths are always wider than the thermal widths, indicating the presence of supersonic nonthermal motions. There are many possible effects that may produce nonthermal line broadening, including infall, rotation, outflow and turbulence. Observations have revealed that molecular clouds have a fragmentary structure. For example, the Ophiucus molecular complex, as traced by 12 CO, exhibits a very filamentary and clumpy distribution. It is fragmented into five main complexes, containing 46 clouds that represent only a small fraction of the total cloud mass (de Geus et al. 1990). A 12 CO survey in the Taurus-Auriga and Perseus complexes reveal that only 10% of the total cloud mass is concentrated in regions of high density gas, while the bulk of the total mass is concentrated in large clouds of low density. The observational results indicate that a molecular cloud, initially containing hundreds or thousands of solar masses of gas, will break, in the course of its evolution, into several fragments. The more massive fragments will continue to collapse and fragment. The smallest objects created in this fragmentation process are the dense cores, whose total mass would only be 5% of the total cloud mass. These dense cores will continue their evolution until form stars Dense cores Dense cores are the densest components of the interstellar medium and are produced whithin the molecular clouds by fragmentation. The mean density of this condensationsis cm 3. Dense gas can be traced by molecular transitions that have a critical density of excitation of order of 10 4 cm 3. These molecules requiere high

41 1.1. Interstellar medium 5 Table 1.2: Physical properties of dense cores in Giant Molecular Clouds and Dark Clouds a GMC Dark Cloud Mass (M ) Size (pc) Density (cm 3 ) Line width (km s 1 ) Temperature (K) a Adapted from Cernicharo (1991) and Mundy (1994) densities to populate collisionally their excited states. The most widely used high density tracers are the CS(2 1) rotational transition and the inversion transition of the (1, 1) metastable level of NH 3. Although other transitions of these molecules and other molecules (HCO +,NH + 2,HCN,HC 3 N...) can be equally used. Dense cores have been found to be intimately related to star-formation. NH 3 observations of isolated dense cores in nearby dark clouds have revealed that dense cores have masses of 1 M (Myers & Benson 1983; Benson & Myers 1989), which is comparable to that of a typical low-mass star. Infrared observations (Beichman et al. 1986; Myers et al. 1987) showed that a significant number these dense cores are associated with infrared sources, suggesting an association between dense cores and young stars. Moreover, the starless cores were identified as potential sites of future isolated low-mass star formation, supporting the idea that stars born in dense cores. All these observational results indicate that there is a close link between the physical properties of the dense gas and its evolution to form a star and provides observational contraints to test models of isolated, low-mass star formation (Shu, Adams & Lizano 1987). Therefore, to understand the molecular cloud evolution and the star formation process, it is essential to understand the density structure of molecular clouds and their dense cores. The main parameters that characterize the physical conditions in dense cores are the temperature and density structure, the velocity field, the mass and the molecular abundances. Magnetic fields are also an important parameter in the evolution of dense cores. In Table 1.2 some of the typical parameters of dense cores are listed.

42 6 Chapter 1. Introduction Shape of dense cores Physical processes that occur in dense cores determine its shape. The shape of dense cores is determined by the self-gravity of the gas they contain and by thermal, turbulent and magnetic pressure. Moreover, since star formation occurs in these dense regions their physical properties are further modified by outflows and winds from the protostar embedded within them. Analysis of core shapes is useful to help describe the physical processes that form, maintain, and destroy cores, and to identify initial conditions for star formation. CS and NH 3 surveys reveled that a typical dense core has an elongated distribution of its total column density, with axial ratio , over sizes scales pc (Myers et al. 1991). The elongation is observed in cores with and without stars (Benson & Myers 1989), and in cores with and without outflows (Torrelles et al. 1983, 1986; Anglada et al. 1989). This result led Myers et al. (1991) to suggest that the core elongation seems to be an initial condition which precedes the star formation rather than a consequence of star formation or outflows. Although results indicate that dense cores are elongated, it is not clear if cores are in general oblate or prolate. Statistics of core map elongation have been interpreted as indicating that most cores have 3-dimensional shape which is prolate, rather than oblate (Ryden 1996). The location of elongated cores in more extended filamentary structures strongly favors the prolate over the oblate interpretation (Lada 1999). However, models of core evolution including strong magnetic fields predict oblate structures (Li & Shu 1996 and references therein). NH 3 observations of several dense cores also favor an oblate structure rather than a prolate (e.g., Torrelles et al. 1994). Line widths The line width of an spectral line cointains information about the velocity dispersion along the line of sight. Since the natural width of an spectral line is very small in the radio domain, the line width of an emission line is principally determined by the Doppler width characteristic of the kinetic temperature of the gas, i.e., the thermal width. The turbulent velocity is determined by the nonthermal line width. There are many possible effects that may produce nonthermal line broadening, including infall, rotation, outflow and turbulence. Molecular line observations of dense cores in Taurus-Auriga and in other smaller clouds indicate that the H 2 molecules in these cores have primarily thermal motions, in contrast with the nonthermal mo-

43 1.2. Evolutionary sequence of young stars 7 tions at larger spatial scales in surrounding gas, and in dense cores associated with regions forming more massive stars. The association of thermal dense cores with low-luminosity IRAS sources leds to suggest that thermal motions may be part of the initial conditions for low-mass stars formation (Myers, Ladd & Fuller 1991). Dense cores have line widths, column densities and sizes which appear to be close to the virial equilibrium (Myers et al. 1991; Harju, Walmsley & Wouterloot 1993), in where the gravitational potencial energy and kinetic energy are approximately equal. The full width at half maximum (FWHM) of the observed line profile ΔV obs is mainly determined by thermal and nonthermal motions. The relation can be written as ΔVobs 2 =ΔVnth 2 +ΔVth, 2 where ΔV rmnth is the FWHM of nonthermal motions, and ΔV th is the FWHM of the Maxwellian distribution of thermal velocities, given by ΔV 2 th = 8ln2kT K m, where m is the mass of the observed specie, T K is the kinetic temperature and k is the Boltzmann s constant. In adequate units, it can be writen as [ ] ΔVth km s 1 [ TK =0.21 K ] 1/2 [ m mh ] 1/2 Line widths constitute a valuable tool for determining the turbulent motions in the cloud. However, it is necessary to know both, kinetic temperature and line width of the line. This analysis could be easily performed with NH 3 observations, because NH 3 permits accurate estimations of both kinetic temperature and observed linewidth (see 1.5). 1.2 Evolutionary sequence of young stars Observations of low-mass cores in Taurus and Ophiuchus (e.g., Benson & Myers 1989) have outlined an scenario in which individual stars form from small, isolated dense cores distributed throughout a molecular cloud. These observations have led to the first detailed theory of star formation (Shu et al. 1987; Shu 1997). A

44 8 Chapter 1. Introduction different picture of star formation emerges from observations of the ρ Ophiuchi molecular cloud (Lada et al. 1993; André et al. 1993), where a rich cluster of stars is forming from a single massive concentration of dense gas. In this case, star formation does not appear to occur in an isolated environment but rather in a clustered one. These differences in star-forming environments have lead to the suggestion that two distinct modes of star formation may exist: an isolated mode and a clustered mode (Lada 1991, Lada et al. 1993). Isolated star formation can be characterized by low stellar density and low-overall star-formation efficiency. In this mode, one to a few stars, usually low-mass stars, form from a small, well-defined dense cores distributed through a molecular cloud (Lada 1987). In the clustered star formation mode groups of many stars, both low and high mass, form from a single massive concentrations of gas. The physical conditions within massive cores producing rich clusters of stars are expected to be quite different from those of isolated cores forming single stars. The isolated mode is the simplest and best studied case, while a generally description for the cluster mode does no exists yet. Low-mass stars are considerably less destructive to their natal environment than high-mass stars, since when massive stars form in the cloud, heat, ionize and disrupt the molecular gas. In a relative short time ( 10 6 years) the massive stars disrupt the entire complex and remove the vast majority of the original mass of the system. If this occurs in a cluster, stars that were initially orbiting in virial equilibrium freely expand into the space, disrupting the rich cluster where they were born. In contrast, low-mass stars can be form in relative isolation and their immediate circumstellar environments are not so strongly influenced by the disruptive presence of nearby stars. On the other hand, low-mass stars are the only stars which have an observable pre-main sequence stage of stellar evolution. Massive stars probably begin to burn hydrogen and reach the main sequence before their protostellar stage of evolution ends, and thus, they are more difficult to observe. The shape of the spectral energy distribution of a young stellar object depends of the nature and the distribution of surrounding material, and then, it varies in function of the state of evolution of a YSO. For low-mass stars, spectral energy distributions allow young stellar objects to be divided into four classes that represent the evolutionary sequence from a protostar to a young main sequence star (Adams, Lada & Shu 1987, André, Ward-Thompson & Barsony 1993) according to the spectral index in the IR α IR = d log(λf λ) d log(λ).

45 1.2. Evolutionary sequence of young stars 9 Fig 1.1 illustrates the spectral energy distribution for each class. These classes or evolutionary stages are: Class 0 sources: Corresponds to the main accretion phase. In this phase a star acquires the bulk of its mass through accretion of surrounding circumstellar material into an embryonic stellar core, but most of mass is still in the form of circumstellar envelope. Class 0 objects are defined by three observational properties (André, Ward-Thomson & Barvainis 2000): (1) There exists a central YSO, evidenciated by, e.g., the detection of a compact cm radio continuum source, a very energetic and highly collimated CO outflow, or an internal heating source. This property distinguishes Class 0 objects from the pre-protostellar cores. (2) Centrally peaked but extended submillimeter continuum emission traces the presence of a spheroidal circumstellar dust envelope. (3) The ratio of submillimeter to bolometric luminosity is elevated (L submm /L bol > 0.5%), where L submm is measured longward of 350 μm suggesting that the mass of envelope exceeds the central stellar mass. Class I sources: These sources are in the late accretion phase (André &Montmerle 1994), but still surrounded by large amounts of circumstellar dust. They are detected in the near-infrared (2.2 μm) and are characterized by α IR > 0. Class I sources are interpreted as relatively evolved protostars, with typical ages years (Kenyon & Hartmann 1995), surrounded by both a disk and a diffuse circumstellar envelope of substellar ( < M ) mass. Most of Class I sources have already accumulated in their centers most of their final stellar mass (André & Montmerle 1994). Class I sources are associated with CO molecular outflows, exhibit an infrared excess and derive an important fraction of their luminosity from accretion. Class II sources: These sources are in the first stage of the pre-main sequence. and are characterized by 1.5 <α IR < 0). They can be observed at optical as well as infrared wavelenghts. Class II sources are interpreted as young stars surrounded by circumstellar disk, but lacking a dense circumstellar envelope (André & Montmerle 1994). Class III sources: These sources are the most evolved objects, basically free of any significant amount of circumstellar gas and dust and characterized by α IR > 1.5. The vast majority of the original star forming material has been either incorporated into the star or removed from its vicinity. They are found

46 10 Chapter 1. Introduction Figure 1.1: Classification of YSOs according to their spectral energy distribution (from Lada 1999). Class 0 and Class III sources have a distribution whose widths are similar to a single temperature blackbody function. Class I and Class II sources display infrared excess which produces energy distributions which are broader than a single blackbody function. The vertical line is for reference, at a wavelenght of 2.2μm. to lie above the main sequence and can be thought as a classical pre-main sequence star. Almost all the low-mass stars probably pass through these stages during their formation, although the duration of each phase may be different for different stars. These classes indicate an evolutionaty sequence in which the young stellar object loss gradually its circumstellar environment. The evolutionary sequence Class 0 Class I Class II Class III requires the progressive removal or dissipation of the circumstellar material in the protostellar infalling envelope and of the circumstellar disk. At some point very early in the YSO evolution the core material from which it grows

47 1.3. Molecular outflows 11 must be physically removed by some active agent. This agent is likely an energetic bipolar outflow. 1.3 Molecular outflows The molecular outflows have velocities ranging from 10 to 30 km s 1, but in some flows, this motion exceeds 100 km s 1. In many cases, these molecular outflows constitute the first observational manifestation of the star-forming event and are detected as broad line wings in the mm-wave emission lines of many molecules, especially the CO molecule. Molecular outflows play an essential role in the star formation process by carrying away the excess of angular momentum from the contracting molecular cloud, and by limiting the mass and size of the protostellar infalling condensation (Shu, Adams & Lizano 1987). The high velocity outflows impact on the molecular cloud dispersing the surrounding material, therefore most of the accelerated mass has been swept up from the molecular cloud that surround the young stellar object rather than originated in mass ejected from it. Molecular outflows continue playing an important role during entire collapse and accretion disk formation stage and they determine the evolution of the dense core where the star was born. Molecular outflows are generated almost exclusively by embedded objects, the Class 0 and Class I sources. Recent observations of the Serpens region indicate that most, if not all, the Class 0 and Class I sources drive molecular outflows (Davis et al. 1999). Outflows emanating from optically visible T Tauri stars are rarely found (e.g. in T Tau, Edwards & Snell 1982) and are poorly collimated compared with the outflows from very young stars. The most characteristic property of molecular outflows is their frequent bipolar geometry, which arise from the presence of two separated lobes of gas, one red shifted and the other blue shifted, with a young stellar object in between. Althogh bipolarity seems a general property, each outflow exhibit its own characteristics, that may reflect differences in the cloud core or in the young stellar object themself. Most outflows exhibit considerable overlap between redshifted and blueshifted lobes. There are outflows where the blue and redshifted lobes are symmetrically displaced on opposite sides of the central YSO (e.g. in L1551; Snell, Loren & Plambeck

48 12 Chapter 1. Introduction Figure 1.2: The CO quadrupolar outflow associated with L723 (from Avery et al. 1990) is an example of the complex structure of outflows. 1980) and on the other hand, there are asymmetric outflows (e.g. in Mon R2; Loren 1981). A few flows are monopolar, probably because the missing lobe is breaking out of the molecular cloud and others show complex geometry (e.g. the quadrupolar outflow in L723, Avery et al. 1990; see Fig. 1.2) that may arise from multiple sources (Anglada et al. 1991) or deflection by dense ambient gas (e.g. in AFGL6366S; Verdes-Montenegro et al. 1989). In some outflows, high-velocity CO emission is confined to shells or to the walls of evacuated cavities. Molecular outflows exhibit different degrees of collimation, but most of them can be separated into two main groups: outflows poorly collimated, known as classical outflows, and outflows extremely collimated (see Fig 1.3). These differences in the outflow collimation are believe to come from the different classes of sources powering these two types of outflows. Outflows highly collimated are believed to be powered by Class 0 YSOs, while outflows powered by Class I objects appear less collimated. These suggest that by the time a YSO reaches the Class I stage, its bipolar outflow has lost an appreciate part of its collimation. A shell structure surrounding an evacuated cavity with a reflection nebula is formed and the optical Herbig-Haro objects become visible. Although, our knowledge about the outflow phenomena has increased in the last few years, through more sensitive observations, there are some questions about mole-

49 1.3. Molecular outflows 13 Figure 1.3: The CO outflow associated with H221 is one of the most highly collimated outflow known to the date (from Gueth & Guilloteau 1999) cular outflows that remain still poor known. One of them is the driving mechanism of the molecular outflows. Several models have been proposed to explain the driving mechanism of outflows. The most commonly accepted are the jet-driven bow shock model and the wind-driven shell model. In the jet-driven bow shock model, a jet propagating into the ambient material cloud forms a bow shock at the head of the jet. As the bow shock moves away from the star, it interacts with the ambient material and produces the molecular outflow around the jet (Raga & Cabrit 1993; Masson & Chernin 1993; Chernin et al. 1994). This model can reproduce well the characteristics of the highly collimated outflows. In the wind-driven shell model the young star blows a radial wind into the ambient material, driving a forward shock that swept up the ambient material producing the molecular outflow (Shu et al. 1991; Li & Shu 1996; Shu et al. 2000). This model can reproduce the classical outflows. Although, neither model can explain enterely all the characteristics of observed molecular outflows (see Lee et al for a comparison between these models), most of the known outflows can be explained by one of this models. Other important issue in the study of the molecular outflows is the identification

50 14 Chapter 1. Introduction of the exciting source. Molecular outflows are generated by a very young star in the early stages of evolution. In these stages the young stellar object is deeply embedded in the dense gas from which it has been formed, rendering undetectable at optical and even infrared wavelengts. The position of the driving sources can be traced by observations of dense gas with high density tracers, like NH 3,sincethe driving source of molecular outflows is usually found close to the position of the NH 3 emission maximum (Anglada et al. 1989). 1.4 Herbig-Haro objects The material ejected from the young stellar objects often manifests in optical wavelenghts as shock-excited emission-line nebula, the Herbig-Haro objects, that often form a large-scale association referred to as HH flows (see Fig. 1.4). The morphological structure of the HH flows, with bow shocks, jets and separated knots, suggests that mass ejection is episodic with eruption events ocurring over long intervals of time. In the last few years, several HH parsec-scale flows have been discovered (e.g. Devine et al and references therein). The HH flows tend to have velocities ranging from 100 to over 600 km s 1, which are much higher than the velocities of molecular outflows. Optical observations reveal that the Herbig-Haro jets generated by YSO s are highly collimated. These optical outflows are generally bipolar in the sense that there are objects moving away from their energy source on both sides of the outflow. The shocks at the end of the jets are reasonably well understood in terms of simple bow-shock models. But the excitation in the jets themselves and the collimation mechanism remain controversial. Because of the highly collimated appearance of the HH objects and specially, the optical and radio jets in the center, it has been suggested that circumstellar disks around YSOs are needed to collimate such outflows (e.g., Calvet, Hartmann & Kenyon 1993). One of the best examples of circumstellar disk around YSOs have been observed through HST observations in HH 30 (see Cotera et al and references therein). Models involving magnetohydrodynamic processes in an accretion disk has been proposed in order to explain the accelaration and collimation of the stellar winds that produce the HH objects and the molecular outflows (Shu et al. 1994; Pudritz et al. 1991). There is a growing belief that highly collimated circumstellar ( 10 4 AU) op-

51 1.4. Herbig-Haro objects 15 Figure 1.4: Image of the jet HH 502, which is embedded in the Orion nebula as observed in H α (right) and [SII] (left)(from Bally and Reipurth 2001) tical jets drive the less collimated (and of lower velocity; > 10 km s 1 ) molecular outflows that extend to larger, interstellar scales ( 10 5 AU). Detailed models have been developed in this line (see, e.g., Raga et al and references therein). In these unified models, a high velocity, collimated wind (which would correspond to the optically detected HH objects or jets) drives an envelope of slower, less collimated material (e.g., environmental material set into motion by viscous coupling), which is identified with the molecular outflow. Within this scenario, both optical and molecular outflows would coexist during the pre-main-sequence stages. Despite this coevality, depending on the evolutionary stage of a particular young stellar object, observations could appear dominated by either type of mass loss phenomenon. For the youngest objects, which are still deeply embedded in high density molecular material, circumstellar optical jets are expected to be highly extinguished and hardly detectable, while molecular outflows can be more prominent. These deeply

52 16 Chapter 1. Introduction Figure 1.5: The HH212 jet as imaged in H μm shock emission. The contours represent the integrated NH 3 (1,1) emission of dense protostellar envelope gas (from Wisseman et al. 2001) embedded flows are more accesible in tracers at longet wavelengths; molecular hydrogen (H 2 ) is an important tracer of shocks at near- to mid- infrared wavelengths (see Fig. 1.5). As the object evolves, the ambient molecular gas is progressively being swept up by the outflow, and the driving jet becomes more easily detectable at optical wavelengths. In these regions of relatively low extintion optical emission typical Herbig-Haro objects can be observed in the Hα and [SII] lines. The decrease of the high density gas near the star is expected to be evidenced through a decrease in the line intensity of high-density tracers, such as the NH 3 molecule. The location and identification of the jets exciting source is a necessary step for studying the propertes of the young stellar object and the jet itself. In addition,

53 1.5. Interstellar ammonia: Its role in the study of dense cores 17 it is necessary to explain the nature of the interaction of the outflows with the surrounding material producing the HH objects. Radio observations of high density tracers, as NH 3 are very useful to determine physical properties of the molecular environment of the exciting source. 1.5 Interstellar ammonia: Its role in the study of dense cores Ammonia was discovered in the interstellar medium by Cheung et al. (1968). It was the second molecule to be identified in the interstellar medium from its radiofrequency spectrum; and because it was the first interstellar polyatomic molecule, ammonia provided initial evidence that conditions were sufficiently favorable in certain parts of the Galaxy for relatively complex molecules to exist in detectable abundances. Nowadays, over a hundred molecules have been discovered, mostly from radio spectral lines. Many of them have several detected lines, and in the stronger lines it is possible to detect lines from isotopic species, such as 13 CO or C 18 O. Many polyatomic molecules have been observed in dense interstellar clouds, where dust grains play an important role in catalysing the reactions that form such molecules. Ammonia has proved to be an invaluable spectroscopic tool in the study of the interstellar medium. Because of its large number of transitions sensitive to a wide range of excitation conditions and the fact that it can be detected in a great variety of regions, NH 3 is perhaps second only to CO in importance. The ammonia molecule has a series of characteristics that makes it very useful for the study of star forming regions. These are the existence of metastable and nonmetastable states, orthoand para- species, inversion motion of the molecule and hyperfine structure. This particular feature of the NH 3 spectrum allows one to determine many of the cloud conditions. One of the most important characteristics is that NH 3 is an excellent high density tracer, requiring densities greater than 10 4 cm 3 to exciting the lowest rotational level, the (J, K) =(1, 1).

54 18 Chapter 1. Introduction Physics of the NH 3 molecule The physics of the NH 3 molecule is well understood (Feynman 1965; Townes & Schawlow 1975; Ho & Townes 1983). The pyramidal NH 3 molecule is a typical example of a symmetric top with inversion. The rotational energy levels are characterized by two quantum numbers J and K, corresponding to the total angular momentum and its projection along the molecular axis. Because of the symmetry, the NH 3 molecule has an electric dipole only along the molecular axis and the dipole selection rules are ΔK = 0andΔJ = 0, ±1. Due to these selection rules, the frequencies observed do not depend in any way on K. Interaction between rotational and vibrational motions, even in the lowest vibrational state, induces a small dipole moment perpendicular to the rotation axis, giving rise to very slow Δk = ±3 (K = k ) transitions; except for this, the K-ladders (states with the same value of K) are normaly independent of each other. Normal intermolecular collisions (not involving weak magnetic effects) also produce only transitions in which Δk is a multiple of 3 (including 0). Within each K-ladder, the upper states (J > K) are called nonmetastable because they can decay rapidly ( s) via the farinfrared ΔJ = 1 transitions. The lowest states (J = K) can only decay via the much slower (10 9 s) Δk = ±3 transitions and are called metastable. It is clear that the nonmetastable states will be difficult to populate under normal astrophysical conditions, while the metastable states can be populated via Δk = 3 collisions. This fact is substantiate by observations. However, in regions with very high temperatures (T kin 200 K) and/or high density (n(h 2 ) 10 7 cm 3 ), several ammonia inversion transitions involving nonmetastable levels with energies 1000 K above the ground state can be detected, some of them as maser-like emission (e.g. Madden et al. 1986; Henkel et al. 1987). Because the possible orientations of the hydrogen spins, two distinct species of NH 3 exists. These are ortho-nh 3 (K =3n, n an integer, all H spins parallel) and para-nh 3 (K 3n, all H spins not parallel). Since normal radiative and collisional transitions do not change the spin orientations, transitions between ortho- and para- NH 3 are forbidden. Several ways to mix both species have been proposed, the time scale for achieving the equilibrium between the two species is very long 10 6 yr (Cheung et al. 1969). This leads to the suggestions that a rotational temperature between ortho- and para-nh 3 may reflect conditions at an earlier time, while a rotational temperature within the same species may reflect more recent conditions.

55 1.5. Interstellar ammonia 19 Figure 1.6: Energy level diagram of rotation-inversion states. J is the total angular momentum quantum number, and K is the projected angular momentum along the molecular axis (from Ho & Townes 1983) An analysis of the para-nh 3 observations was made by Kuiper (1994). Based on this, Kuiper et al. (1995) determine the evolutionary state of the NGC 6334 cloud core in base of the analysis of the relative abundance of the two species of ammonia. In addition to rotation, NH 3 molecule also undergoes vibrational motion. The N atom can tunnel quantum mechanically through the plane of the H atoms. The potential barrier due to the H atoms is low enough that such tunneling occurs rapidly, resulting in the two lowest vibrational states providing a transition frequency that falls in the microwave range. All (J, K) rotational states are splitted into two inversion doblets (see Fig. 1.6), except for rotational states with K =0wherenuclear spin statistics and symmetry considerations eliminate half of the inversion doublet. The transitions across the doublets of rotational states with ΔJ =0,ΔK =0are allowed from symmetry considerations and they fall into the range between GHz ( 1.3 cm). Observations of these inversion transitions constitute the bulk of the information on interstellar NH 3.

56 20 Chapter 1. Introduction The electric quadrupole interaction between the N nucleus and the eletron charge distribution produces an hyperfine splitting of the inversion levels. Each level of the doublet is splitted by nuclear orientation into 3 hyperfine states characterized by the quantum number F 1, which represents the total angular momentum including the nitrogen spin I N,thusF 1 = J + I N and the possible values are F 1 = J +1,J,J 1. All the (J, K) rotational levels suffer this electric quadrupolar split, except those levels with K = 0. The transitions between these quadrupolar levels are produced following the selection rules ΔF 1 =0,ΔJ =0andΔK =0. Forthe(1, 1) rotational level the frequency separation between these 3 sublevels is 1 MHz, while for the higher rotational levels, (J, K) > (1, 1) is about 2 MHz. The selection rules for the (1, 1) level produce 6 transitions, thus the transitions with ΔF 1 =0andF 1 =0 are forbidden, while for the others rotational levels 7 transitions are produced. The transitions for which ΔF 1 = 0 have the same frequency, the net effect of this is that the spectrum consists in one central line corresponding to ΔF 1 =0andtwopairsof satellite lines corresponding to ΔF 1 = ±1 symmetrically spaced about the unshifted mainfeature(seesepúlveda 1993 and references therein for further details). The satellite lines are larger for the (1, 1) line, for which the combined intensity of the four satellite lines is approximately equal to that of the main feature. In fact, the main line has approximately the 50% of the transition total intensity, while the internal satellites have 14% each one and the external satellites have only about 11% of the total intensity. The relative intensity of the satellite components falls off rapidly with increasing J. Forthe(2, 2) line, the main line has the 80% of the total intensity and the satellites only 5% each one; and for the (3, 3) line, the intensity of the main line is the 90% of the total intensity. This decreasing of the intensity of the satellite lines for higher levels make very difficult their detection in the typical conditions of the interstellar medium. However, in warm compact cores this hyperfine structure of metastable levels can be detected, e.g., Garay & Rodríguez (1990) and Garay, Moran & Rodríguez (1993) have detected the hyperfine structure of the (2, 2) and the (3, 3) inversion transitions in ultracompact H II regions; and the hyperfine structure of the (4, 4) was detected by Wilson et al. (2000) in observations of the Orion Hot Core. These hyperfine components are further splitted by weaker magnetic interactions due to the I N J and I J coupling (I N = nitrogen spin, I = sum of hydrogen spins), and the H-N and H-H spin-spin interactions. The result of these magnetic interaction is to split each F 1 levels into two sublevels, except the F 1 =0levelwhich

57 1.5. Interstellar ammonia 21 is not splitted. In other words, the 3 electric hyperfine components are splitted into 5 magnetic hyperfine components characterized by the quantum number F = F 1 + I H. The transition rules between these magnetic hyperfine components are ΔK =0,ΔJ =0andΔF =0, ±1. For K =1,theI J and H-N interactions have unequal effects on the upper and lower levels of the inversion line, producing a hyperfine doubling on the order of 40 khz. The other magnetic interactions produce splittings on the order of only 10 khz. The net result of these interactions is to split the (1, 1) inversion line into 18 distinct hyperfine components, since the transitions with ΔF = 0andF = 0 are again forbidden (see Sepúlveda 1993 and references therein for further details). In the conditions of the intestellar medium, the five hyperfine lines of the NH 3 spectrum have line widths greater than 1 km s 1,and for the lower metastable states can be detected easily. The high-order magnetic hyperfine structures with velocity separation between km s 1 are usually not resolvables. However, in several conditions in dark clouds even the magnetic hyperfine components have been resolved (Ho et al. 1977; Myers & Benson 1983; Anglada et al. 1995) NH 3 in dense cores The detection of the (J, K) =(1, 1), (2, 2) and (3, 3) inversion lines of NH 3 in cool nearby dark clouds was first reported by Morris et al. (1973). Although their observations were carried out with very low resolution, they provided strong evidence that NH 3 is a widespread constitute of interstellar molecular clouds. With these observations they opened a new way for study the dense cores in molecular clouds through the observations of the NH 3 emission. Barret, Ho & Myers (1977) from multitransition observations of the Kleinmann-Low nebula have demostrated that the molecular observations are extremely useful in examining the physical conditions of dense gas and its kinematics structure, and that the NH 3 observations are a very useful tool to determine the kinetic temperatures and the density of the globules. Since these first observations, NH 3 observations have been used to study the properties of dense cores. The relationship between dense cores and star formation, was established from NH 3 surveys of dense cores in dark clouds, which revealed that a large number of dense cores have associated infrared sources and those without infrared sources are in the process of forming stars (Myers & Benson 1983; Benson & Myers 1989).

58 22 Chapter 1. Introduction From NH 3 observations several important physical parameters of dense cores, such as optical depth or excitation temperature, can be obtained without observing different isotopes as other high density tracers as CS or HCO +. In addition, several NH 3 rotation inversion transitions have frequencies close to that of the (J, K) =(1, 1) line, this allows a more sophisticated multilevel analysis using the same telescope with the same receiver, beam size and system temperature. Moreover, from the ratio of two different inversion transition lines, a good estimation of the kinetic temperature of the gas can be obtained and therefore, obtain information about possible heating of gas in the vicinity of young stellar objects. Statistical studies show a close association of the ammonia emission maximum with the powering sources of outflows (Torrelles et al. 1983; Anglada et al. 1989). For all these reasons, observations of ammonia are very useful to help determine the physical conditions and structure of the densest cores of molecular clouds and, taking into account that the stars begin their lives deeply embedded in the high density gas, the observations of the dense cores provide a great knowledge about the physical conditions of the star-forming regions and about all the phenomena related with this process. In particular, ammonia observations have been useful to study and better understand the outflow phenomena that accompanies the earliest stages of protostellar evolution. Single-dish ammonia observations have been proven to be a powerful tool for studying the distribution, the global properties and the physics of dense cores at large-scale. Different issues related to the star-forming regions and to the process related with them have been studied through this kind of observations, among them: NH 3 surveys help to determine the distribution of dense gas cores within giant molecular clouds. For example, from an NH 3 survey of dense cores in the W 3 main cloud, Tieftrunk et al. (1998) found that only the 20 % of the molecular gas in the surveyed region is forming dense cores, suggesting that dense cores fill only a small fraction of the total mass of the giant molecular cloud and that they are concentrated in regions of active star formation. NH 3 single-dish surveys are useful to compare different sites of star formation. From an NH 3 survey of isolated dark globules, Bourke et al. (1995) found that globules are less dense and less active sites of star formation than cores within the complex, suggesting that the presence of either external mass or a significant stellar wind, plays an important role in initiating the star formation

59 1.5. Interstellar ammonia 23 process. Single-dish NH 3 surveys was used to compare the physical characteristics of dense clumps in regions of high and low-mass star formation. Through observations of dense cores in Orion, Cepheus, Taurus and Perseus several differences in the NH 3 linewidth, temperature and mass have been found. These differences were interpreted as indicators of different modes of star-formation in each region, high-mass, low-mass or intermediate (Harju et al. 1993; Ladd et al. 1994). NH 3 is useful to determine the physical conditions in star-less cores. The observations of NH 3 self-gravitating clumps without signs of star-formation, could establish an ideal laboratory to study pre-collapsing physical conditions, preceding the new star formation (Gómez et al. 2000) Torrelles et al. (1983) from an NH 3 survey of molecular outflow sources have concluded that the bipolar outflows are commonly associated with high-density condensations, which are near the virial equilibrium and have internal velocity dispersions larger than those of dark clouds. The high-density condensations associated with the bipolar outflows are generally elongated and centered at the position of the suspected exciting source and may play an important role in the outflow collimation at large scale. Anglada et al. (1989) from a survey of outflow sources, both molecular and optical, also concluded that the exciting sources of molecular outflows are usually embedded in the high-density gas and located very close ( < 0.1 pc) to the ammonia emission peak. In this sense, and at this scale, single-dish ammonia observations can be an important tool for constraining the location of the exciting sources, or for discriminating among several exciting source candidates (e.g. in AFGL 5157; Torrelles et al. 1992). The physical association of powering sources and dense molecular structures is confirmed by the perturbation of the high-density gas that is produced by strong stellar winds and stellar photons from the embedded powering source. Such perturbations can be observed as broadening of lines associated with outflows and local heating of the molecular gas (Myers et al. 1988). Ammonia is a good tracer of such perturbations, because the kinetic temperature can be estimated from the observation of two different rotational transitions (see 1.5.1). High-angular resolution ammonia observations have been proven to be a powerful tool for studying, at higher degree of angular resolution and sensitivity, the high-

60 24 Chapter 1. Introduction density molecular gas in star-forming regions. These observations are normally carried out in regions previously mapped in single-dish. Different and important issues related to this topic have been pursued through this kind of observations, among them: The location and identification of deeply embedded YSOs through kinetic temperature maps obtained from the observed ammonia line emission. In this way, e.g., Girart et al. (1997) detected a hot spot in L723, which is proposed to be due to the presence of an embedded very young stellar object. This object is suggested as the driving source of the smaller pair of molecular outflow lobes; Gómez et al. (1994) identified the exciting source of the molecular outflow in NGC The search for thick disklike molecular structures around YSOs and their role in the collimation of the molecular outflows. This search is done by performing spatio-kinematical studies to characterize the velocity field in these elongated structures, (if they are rotating, contracting/expanding...). These structures are related to one of the major fields of interest in current astronomy, since planetary systems are believed to be originated from circumstellar disks ( 100 AU) within these thick disklike molecular structures ( > 1000 AU). This search has been successful in several regions, e.g. L1448C is surrounding by disklike structure possibly self-gravitating with a velocity structure that may be interpreted as both rotation and radial contraction motions (Curiel et al. 1999). Torrelles et al. (1994) find a distribution of density gas in the HH 1-2 region that is consistent with a contracting self-gravitating interstellar toroid. The characterization of the interaction of YSOs and their associated outflows with dense gas, e.g. in terms of heating and broadening of ammonia lines. In this sense, in Serpens FIRS1 the high-velocity ammonia emission detected was interpreted as molecular gas entraining along the wall of the cavity left by a radio continuum jet (Curiel et al. 1996). Source HH34 IRS is surrounded by a cavity created by its stellar wind. The cavity is embedded in a larger scale high-density structure traced by single-dish ammonia emission (Anglada et al. 1995). Bow-shocks are detected in the ammonia emission towards the L1157 outflow (Tafalla & Bachiller 1995) The identification of signatures of gravitational collapse. Keto, Ho & Haschick (1987) found that the molecular core surrounding the H II region G

61 1.6. Main goals of this work 25 appears gravitationally collapsing onto the H II region. In the massive starforming region DR 21, the dense structure was resolved into two isolated dense cores that may represent molecular cloud condensations in the earliest stages of stellar evolution undergoing gravitational collapse and accretion, just prior to the formation of massive stars (Keto 1990). 1.6 Main goals of this work The main goals of this work are to study the relationship between high-density gas, molecular and optical outflows and their exciting sources and study the propierties of the high-density gas associated with young stellar objects. In order to carried out our purposes, we have study the ammonia emission towards a wide sample of star-forming regions associated with molecular and optical outflows. In addition, we have carried out a more deeply study of two selected sources of our sample. The region associated with IRAS has been observed at different wavelengths, in addition to the ammonia observations. In the region L1287, we have carried out high resolution VLA NH 3 observations in order to better establish the structure of this region at small scale. The structure of the work is as follows: In Chapter 2, we present single-dish ammonia observations of a wide sample of star formation regions associated with molecular or optical outflows. We have study each source individually, mapping the ammonia emission. We have derived physical parameters of the dense gas and discuss in each case the possible location of the exciting source. In adittion to this individual study, we made an statitistical study in order to determine the relationship between the dense gas, as traced by the ammonia emission, and the nature of the outflow. The results of several sources of the sample have been published in Anglada, Sepúlveda & Gómez (1997). In Chapter 3, we present the results of near-ir images, 1.3 mm continuum emission and ammonia line observations of the source IRAS We discuss the morphology of the infrared nebula detected, we obtain the infrared energy distribution and study the distribution of dense gas. We derive physical parameters of the dense gas and study the relationship between dense gas and the young object. The results of this chapter have been published in Persi et al. (1994)

62 26 Chapter 1. Introduction In Chapter 4, we present the results of high resolution VLA ammonia observations of the region L1287. With these observations we have studied the structure of the dense gas at small scale, in order to determine the exciting source of the molecular outflow and to determine the physical conditions of the dense gas associated with the young stellar objects that are detected in this region. Finally, we present the Conclusions we reached from our overall study.

63 Bibliography Adams, F.C., Lada, C.J., Shu, F.H. 1987, ApJ, 312, 788 André, P., Montmerle, T. 1994, ApJ, 420, 837 André, P., Ward-Thompson, D., Barsony, M. 1993, ApJ, 406, 122 André, P., Ward-Thompson, D., Barsony, M. 2000, in Protostars and Planets IV, eds. V. Mannings, A.P. Boss, & S.S. Rusell, Tucson, University of Arizona Press, p. 59 Anglada, G., Rodríguez, L.F., Torrelles, J.M., Estalella, R., Ho, P.T.P., Cantó, J., López, R., Verdes-Montenegro, L. 1989, ApJ, 341, 208 Anglada, G., Estalella, R., Rodríguez, L.F., Torrelles, J.M., López, R., Cantó, J. 1991, ApJ, 376, 615 Anglada, G., Estalella, R., Mauersberger, R., Torrelles, J.M., Rodríguez, L.F., Cantó, J., Ho, P.T.P., D Alessio, P. 1995, ApJ, 443, 682 Anglada, G., Sepúlveda, I., Gómez, J.F., 1997, A&AS, 121, 255 Avery, L.W., Hayashi, S.S., White, Glenn J., 1990, ApJ, 357, 524 Bally, J., Reipurth, B., ApJ, 2001, 546, 299 Barret, A.H., Ho, P.T.P., Myers, P.C. 1977, ApJ, 211, L39 Beichman, C.A., Myers, P.C., Emerson, J.P., Harris, S., Mathieu, R., Benson,P.J., Jennings, R.E. 1986, ApJ, 307, 337 Benson, P.J., Myers, P.C. 1989, ApJS, 71, 89 Blitz, L., Thaddeus, P. 1980, ApJ, 241,

64 28 BIBLIOGRAPHY Bourke, T.L., Hyland, A.R., Robinson, G., James, S.D., Wright, C.M., 1995, MNRAS, 276, 1067 Calvet, N., Hartmann, L., Kenyon, S.J., 1993, ApJ, 402, 623 Cernicharo, J., 1991, in The Physics of Star Formation and Early Stellar Evolution, Eds. C.J. LadaandN.D. Kylafis, Kluwer Academic Publishers, p. 287 Cotera, A.S., Whitney, B.A., Young, E., Wolff, M.J., Wood, K., Povich, M., Schneider, G., Rieke, M., Thompson, R., 2001 ApJ, 556, 958 Curiel, S., Rodríguez, L.F., Gómez, J.F., Torrelles, J.M., Ho, P.T.P., Eiroa, C. 1996, ApJ, 456, 677 Curiel, S., Torrelles, J.M., Rodríguez, L.F., Gómez, J.F., Anglada, G. 1999, ApJ, 527, 310 Chernin, L.M., Masson, C.R., Pino, E.M.G.D.,Benz, W. 1994, ApJ, 426, 204 Cheung, A.C., Rank, D.M., Townes, C.H., Thornton, D.D., Welch, W.J. 1968, Phys.Rev.Lett., 21, 1701 Cheung, A.C., Rank, D.M., Townes, C.H., Knowles, S.H., Sullivan, W.T.III. 1969, ApJ, 157, L13 Davis, C.J., Matthews, H.E., Ray, T.P., Dent, W.R.F., Richer, J.S. 1999, MN- RAS, 309, 141 de Geus, E.J., Bronfman, L, Thaddeus, P. 1990, A&A, 231, 137 Devine, D., Reipurth, B., Bally, J., Balonek, T.J. 1999, ApJ, 117, 2931 Edwards, S., Snell, R. L., 1982 ApJ 261, 151. Feynman, R.P. 1965, The Feynmann Lectures on Physics, Quantum Mechanics, Volume III, ed. Addison-Wesley, California Institute of Technology Garay, G., Rodríguez, L.F. 1990, ApJ, 362, 191 Garay, G., Moran, J.M., Rodríguez, L.F. 1993, ApJ, 413, 582 Gatley I., Becklin, E.E., Sellgren, K., Werner, M.W. 1979, ApJ, 233, 575

65 BIBLIOGRAPHY 29 Girart, J.M., Estalella, R., Anglada, G., Torrelles, J.M., Ho, P.T.P., Rodríguez, L.F. 1997, ApJ, 489, 734 Gómez, J.F., Curiel, S. Torrelles, J.M., Rodríguez, L.F., Anglada, G., Girart, J.M., 1994, ApJ, 436, 749 Gómez, J.F., Trapero, J., Pascual, S., Patel, N., Morales, C., Torrelles, J.M. 2000, MNRAS, 314, 743 Gueth, F., Guilloteau, S. 1999, A&A, 343, 571 Harju, J., Walmsley, C.M., Wouterloot, J.G.A. 1993, A&AS, 98, 51 Henkel, C. Wilson, T.L., Mauersberger, R. 1987, A&A, 182, 137 Ho, P.T.P., Townes C.H. 1983, ARA&A, 21, 239 Ho, P.T.P., Martin, R.N., Myers, P.C., Barret, A.L. 1977, ApJ, 215, L29 Kenyon, S.J., Hartmann, L. 1995, ApJS, 101, 117 Keto, E.R. 1990, ApJ, 350, 722 Keto, E.R., Ho, T.P.T., Haschick, A.D. 1987, ApJ, 318, 712 Kuiper, T.B.H. 1994, ApJ, 433,712 Kuiper, T.B.H., Peters III, W.L., Foster, J.R., Gardner, F.F., Whiteoak, J.B. 1995, ApJ, 446, 692 Lada, C.J., 1987, in Star forming regions, IAUS115, Dordrecht, Reidel Publishing Co, Tokyo, p.1 Lada, C.J., 1991, in The Physics of Star Formation and Early Stellar Evolution, NATO ASIC Proc. 342, eds. Charles J. Lada and Nikolaos D.Kylafis., Dordrecht: Kluwer, p. 329 Lada, C.J., 1999, in The Origin of Stars and Planetary Sistems. Eds, C.J. Lada & N.D. Kylafis. Kluwer Academic Publishers, p. 143 Lada, C.J., Young, E.T., Green, T. 1993, ApJ, 408,471 Ladd, E.F., Myers, P.C., Goodman, A.A. 1994, ApJ, 433, 117

66 30 BIBLIOGRAPHY Lee, C.-F., mundy, L.G., Reiputh, B., Ostriker, E.C., Stone, J.M., 2000, ApJ, 542, 925 Li, Z.-Y., Shu, F.H. 1996, ApJ, 472, 211 Loren, R.B. 1981, ApJ, 249, 550 Madden, S.C., Irvine, W.N., Matthews, H.E., Brown, R.D., Godfrey, P.D. 1986, ApJ, 300, L79 Masson, C.R., Chernin, L.M., 1993, ApJ, 414, 230 Myers, P.C., Benson, P.J. 1983, ApJ, 266, 309 Myers, P.C., Fuller, G.A., Mathieu, R.D., Beichmann, C.A., Benson, P.J., Schild, R.E., Emerson, J.P., 1987, ApJ, 319, 340 Myers, P.C., Heyer, M., Snell, R.L., Goldmisth, P.F. 1988, ApJ, 324, 907 Myers, P.C. Fuller, G.A., Goodman, A.A., Benson, P.J., 1991, ApJ, 376, 561 Myers, P.C., Ladd, E.F., Fuller, G.A., 1991, ApJ, 372, L95 Morris, M., Zuckerman, B., Palmer, P., Turner, B.E. 1973, ApJ, 186, 501 Mundy, L.G., 1994, in Clouds, Cores, and Low Mass Stars, ASP Conference Series, Vol. 65, eds. D.P. Clemens and R. Barvainis, p. 35 Persi, P., Ferrari-Toniolo, M., Marenzi, A.R., Anglada, G., Chini, R., Kruegel, E., Sepúlveda, I., 1994 A&A, 282, 233 Pudritz, R.E., 1991, in The Physics of satar Fromation and Early Stellar Evolution, eds. C.J. Lada and N.D. Kylafis, NATO ASI Series, Kluwer, Dordrecht, 365 Raga, A., Cabrit, S. 1993, A&A, 278, 267 Ryden, B. 1996, ApJ, 471, 822 Sepúlveda, I. 1993, Tesis de Licenciatura, Universitat de Barcelona Shu, F.H. 1997, in IAU Symposium 178, Molecules in Astrophysics: Probes and Processes, ed. Ewine F. Van Dishoeck, p. 19 Shu, F.H., Adams, F.C., Lizano, S. 1987, ARA&A, 25, 23

67 BIBLIOGRAPHY 31 Shu, F.H., Ruden, S.P., Lada, C.J., Lizano, S. 1991, ApJ, 370, L31 Shu, F.H., Najita, J., Ostriker, E., Wlikin, F., Ruden, S., Lizano, S., 1994, ApJ, 429, 781 Shu, F.H., Najita, J., Shang, H., Li, Z-Y, 2000, in Proptostar and Planets IV, ed. V. Manning, A.P. Boss, & S.S. Russel, (Tucson: University of Arizona Press), p. 789 Snell, R.L., Loren, R.B., Plambeck, R.L., 1980, ApJ, 239, L17 Tafalla, M., Bachiller, R. 1995, ApJ, 443, L37 Torrelles, J.M., Rodríguez, L.F., Cantó, J., Carral, P., Marcaide, J.M., Moran, J.M., Ho, P.T.P. 1983, ApJ, 274, 214 Torrelles. J.M., Ho, T.P.T., Moran, J.M., Rodríguez, L.F., Cantó, J. 1986, ApJ, 307, 787 Torrelles, J.M., Eiroa, C., Mausberger, R., Estalella, R., Miranda, L.F., Anglada, G., 1992, ApJ, 384,528 Torrelles, J.M., Gómez, J.F., Ho, P.T.P., Rodríguez, L.F., Anglada, G., Cantó, J. 1994, ApJ, 435, 290 Townes, C.H., Schawlow, A.L. 1975, Microwave Spectroscopy, New York, Dover Publications, Inc. Tieftrunk, A.R., Megeath, S.T., Wilson, T.L., Rayner, J.T. 1998, A&A, 336, 991 Verdes-Montenegro, L., Torrelles, J.M., Rodríguez, L.F., Anglada, G., López, R., Estalella, R., Canto, J., Ho, P.T.P. 1989, ApJ, 346, 193 Wilson, T.L., Gaume, R.A., Gensheimer, P., Johnston, K.J. 2000, ApJ, 538, 665 Wiseman, J., Wootten, A., Zinnecker, H., McCaughrean, M. 2001, AJ, 550, 87

68 32 BIBLIOGRAPHY

69 Chapter 2 Ammonia observations towards molecular and optical outflows 2.1 Introduction The early stages of stellar evolution are dominated by processes involving strong mass loss. The effect of this mass outflow on nearby molecular cloud material is evidenced principally by the presence, in the radio domain, of molecular outflows and, in the optical domain, by the presence of Herbig-Haro objects and highly collimated jets. These mass-loss processes have been proposed as a way to eliminate the excess of material, to eliminate the excess of angular momentum and to regulate the IMF (Shu, Adams & Lizano 1987). Several lines of evidence indicate that molecular outflow is one of the earliest observable phases of the stellar evolution (e.g., Rodríguez 1990). Recent studies indicate that most, if not all, the Class 0 and Class I sources drive molecular outflows (Davis et al. 1999). Likewise, Eiroa et al. (1994a) and Persi et al. (1994) (see also Chapter 2) concluded that an important fraction of what are thought to be the youngest objects (the so-called Class 0 sources; André et al. 1993) are associated with Herbig-Haro objects, suggesting that not only the molecular outflows but also the optical ones start in the early stages of the star formation process. One of the remaining open questions regarding the outflow phenomenon is that of the driving mechanism of molecular outflows. There is a growing belief that highly collimated (moving at high velocity; > 100 km s 1 ) circumstellar ( 10 4 AU) 33

70 34 Chapter 2. Ammonia towards molecular and optical outflows optical jets drive the less collimated (and of lower velocity; > 10 km s 1 ) molecular outflows that extend to larger, interstellar scales ( 10 5 AU). Detailed models have been developed in this line (see, e.g., Raga et al and references therein). In these unified models, a high velocity, collimated wind (which would correspond to the optically detected HH objects or jets) drives an envelope of slower, less collimated material (e.g., environmental material set into motion by viscous coupling), which is identified with the molecular outflow. Within this scenario, both optical and molecular outflows would coexist during the pre-main-sequence stages. Despite this coevality, depending on the evolutionary stage of a particular young stellar object, observations could appear dominated by either type of mass loss phenomenon. For the youngest objects, which are still deeply embedded in high density molecular material, circumstellar optical jets are expected to be highly extinguished and hardly detectable, while molecular outflows can be more prominent. As the object evolves, the ambient molecular gas is progressively being swept up by the outflow, and the driving jet becomes more easily detectable at optical wavelengths. The decrease of the high density gas near the star is expected to be evidenced through a decrease in the line intensity of high-density tracers, such as the NH 3 molecule. Another important issue in the outflow study is the identification of the outflow exciting sources. These sources are commonly embedded in high-density gas, and located near the position of the emission maximum of high-density tracers like the NH 3 lines, as shown by Anglada et al. (1989). This association, at a scale < 0.1 pc, between the ammonia emission peak and the outflow exciting source does not contradict the fact that the ammonia emission could present a much smaller scale structure near the object (e.g., cavities), as revealed by very high angular resolution observations (see the discussion by Anglada et al. 1995, and Chapter 4). Thus, single-dish ammonia observations can be an useful tool to help to establish the position of an outflow exciting source, to confirm a given candidate or to discriminate between several candidates. In order to further investigate these issues, we selected a sample of 53 starforming regions with signs of outflow activity, and we mapped with the Haystack 37 m telescope the NH 3 emission around the position of the suspected outflow exciting sources. Additionally, 15 sources were searched for H 2 O maser emission. Here we present the results of this study. In Sect. 2.2 we describe the observations, in Sect. 2.3 we discuss the sources individually, in Sect. 2.4 we discuss the global results of our study, and in Sect. 2.5 we give our conclusions.

71 2.2. Observations Observations The data presented in this chapter were obtained in two main observational programs. In the first set of observations, carried out in 1990, a sample of 15 regions was observed in NH 3. The sample was enlarged by observing 38 new regions, as well as some additional positions for some of the sources of the first sample, in a second set of NH 3 observations carried out from 1993 to Thus, a total of 53 outflow regions were observed in NH 3. Additionaly, H 2 O maser emission was searched for in 15 regions observations The observations were carried out on February 1990 with the 37 m radio telescope at Haystack Observatory 1. We observed the (J, K) = (1,1) and the (J, K) =(2,2) inversion transitions of the ammonia molecule. At the frequency of these transitions ( GHz and GHz, respectively), the beam size of the telescope is 1. 4, and its beam efficiency at an elevation of 45 was We used a dual maser receiver and both polarizations were observed. The spectrometer was a lag digital autocorrelator with an effective bandwidth of 6.67 MHz. The calibration was made with the standard noise-tube method. The observations were made in the position switching mode. All the spectra were corrected for the elevation-dependent gain variations and for atmospheric attenuation. The rms pointing error was estimated to be 15 by observing continuum unresolved sources. System temperature ranged from 70 to 150 K. The data were reduced using the CLASS and GREG packages of IRAM. The observed spectra were smoothed, resulting a velocity resolution of 0.2 km s 1. We searched 15 sources for NH 3 (1,1) emission. In all cases, we first made measurements on a five-point grid centered at the positions given in Table 2.1, with a full beam separation between points. The NH 3 (1,1) line was detected in 14 of these sources. The NH 3 (2,2) line was observed in 8 sources, at the positions given in Table 2.2, and was detected in 6 of them. Spectra of the NH 3 (1,1) and NH 3 (2,2) lines obtained at the positions given in Table 2.2 are shown in Figs. 2.1 and 2.2, 1 Radio Astronomy at Haystack Observatory of the Northeast Radio Observatory Corporation is supported by the National Science Foundation

72 36 Chapter 2. Ammonia towards molecular and optical outflows Table 2.1: Sources observed in NH 3 or H 2 O in 1990 Source Central position Outflow Excitation Ref. Distance Ref. NH 3 NH 3 H 2O H 2O ff(1950) ffi(1950) type a source b (pc) detected? sensitiv. c detected? sensitiv. c IRAS d 00 h 21 m 22 ṣ ffi CO IRAS No 1.6 IRAS e 00 h 25 m 59 ṣ ffi CO IRAS No 2.4 RNO h 29 m 32 ṣ ffi CO, HH IRAS 2, 3, Yes HH h 31 m 06 ṣ 3 06 ffi CO, HH IRAS 5, Yes HH h 31 m 44 ṣ 7 06 ffi HH Hff? Yes HH 86/87/88 05 h 33 m 15 ṣ 9 06 ffi HH? Yes L1641-N 05 h 33 m 52 ṣ 7 06 ffi CO IRAS Yes L h 13 m 03 ṣ 9 20 ffi CO IRAS Yes L h 14 m 50 ṣ 6 04 ffi CO IRAS Yes L673 f 19 h 18 m 01 ṣ ffi CO IRAS Yes IRAS h 18 m 50 ṣ ffi CO IRAS 10 < ο Yes 0.03 Yes 0.8 L h 58 m 14 ṣ ffi CO, HH IRAS 11, Yes 0.01 No 1.6 L h 33 m 24 ṣ ffi CO IRAS No HHL h 43 m 18 ṣ ffi CO, HHL IRAS 14, Yes 0.03 No 0.8 S140-N 22 h 17 m 58 ṣ ffi CO, HH IRAS 16, No 0.5 IRAS g 22 h 34 m 22 ṣ ffi CO, HH IRAS 18, Yes 0.03 No 1.6 IRAS g 22 h 37 m 40 ṣ ffi CO, HH IRAS 18, Yes 0.03 No 1.6 L h 23 m 48 ṣ ffi CO IRAS 21, Yes 0.04 No 1.6 a CO = CO outflow; HH = Herbig-Haro outflow; HHL = Herbig-Haro-like object b IRAS = IRAS point source; Hff =Hff emission star. c 1-ff rms in the antenna temperature per spectral channel. d Source in the M N region. See x2.3.1 for NH 3 data. e Source in the M N region. See x2.3.1 for NH 3 data. f Additional NH 3 data were obtained in May1996 (see Table 2.4). g Source in the L1251 region. Additional NH 3 data were obtained in May1996 (see Table 2.4). References: (1) Fukui 1989; (2) Edwards & Snell 1984; (3) Cabrit et al. 1988; (4) Jones et al. 1984; (5) Reipurth 1989; (6) Ballyet al. 1994; (7) Fukui et al. 1988; (8) Parker et al. 1988; (9) Armstrong & Winnewisser 1989; (10) Little et al. 1988; (11) Ballyet al. 1995; (12) Haikala & Laureijs 1989; (13) Smith et al. 1989; (14) Dobashi et al. 1993; (15) Gyulbudaghian et al. 1987; (16) Fukui et al. 1986; (17) Eiroa et al. 1993; (18) Sato & Fukui 1989; (19) Balázs et al. 1992; (20) Eiroa et al. 1994b; (21) Terebeyet al. 1989; (22) Yang et al. (1990); (23) Maddalena & Morris 1987; (24) Reipurth 1994; (25) Chen et al. 1993; (26) Reipurth & Gee 1986; (27) Ladd et al. 1991a; (28) Herbig & Jones 1983; (29) Smith & Fisher 1992; (30) Berrilli et al. 1989; (31) Kun & Prusti 1993; (32) Parker et al (K) (Jy) respectively. In Table 2.2 we give NH 3 (1,1) and (2,2) line parameters obtained from a multicomponent fit to the observed spectra at the position of the emission peak, using the CLASS package. Additionally, we searched for the H 2 O maser line (at the rest frequency of GHz) in nine sources. We made five or seven-point maps centered at the positions given in Table 2.1. For the water maser observations, we used the same spectrometer with the same bandwidth as for the ammonia observations. We reached a typical sensitivity of 1.5 Jy (1σ) per spectral channel. We detected H 2 O maser emission towards the region associated with the source IRAS and the spectrum obtained is shown in Fig For the other observed sources we do not detect any significant (> 3σ) H 2 O emission.

73 2.2. Observations 37 Figure 2.1: Spectra of the (J, K)=(1,1) inversion transition of the NH 3 molecule towardsthepositionsgivenin Table 2.2, for the sources detected in the 1990 observations. The vertical axis is the main beam brightness temperature and the horizontal axis is the velocity with respect to that of the center of the main line (given in Table 2.2)

74 38 Chapter 2. Ammonia towards molecular and optical outflows Table 2.2: NH 3 line parameters of sources observed in 1990 a Source Position b (J;K) c V LSR T MB (m) d V e f fi m g Afi m N(J;K) h (arcmin) (km s 1 ) (K) (km s 1 ) (K) (10 13 cm 2 ) RNO 43 ( 1:4; 0) (1,1) +10:26 ± 0:03 0:46 ± 0:06 0:63 ± 0:07 1:1 ± 0:3 0:80 ± 0:08 1:4 HH 83 (0,0) (1,1) +6:22 ± 0:05 0:46 ± 0: » 2 i j j HH 84 (0,0) (1,1) +8:3 ± 0:2 0:3 ± 0: » 3:6 i j j HH 86/87/88 (1.4,1.4) (1,1) +8:88 ± 0:03 0:57 ± 0:06 0:72 ± 0:05 0:1 ± 0:1 0:73 ± 0:04 1:5 L1641-N (1:4; 2:8) (1,1) +6:94 ± 0:01 2:7 ± 0:1 0:92 ± 0:03 1:9 ± 0:2 6:0 ± 0:3 15 L100 (0; 0) (1,1) +1:64 ± 0:08 0:5 ± 0: » 3 i j j L483 (0; 0) (1,1) +5:434 ± 0:003 4:54 ± 0:09 0:57 ± 0:01 4:7 ± 0:1 19:9 ± 0:3 32 (0; 0) (2,2) +5:41 ± 0:03 0:74 ± 0:06 0:79 ± 0:06 0:2 ± 0:1 0:9 ± 0:4 0:9 L673 l (0; 2:8) (1,1) +6:94 ± 0:01 2:1 ± 0:1 0:49 ± 0:02 1:7 ± 0:3 4:9 ± 0:4 6:7 (1:4; 0) (2,2) -» 0:17 k IRAS (0; 0) (1,1) +1:57 ± 0:01 2:66 ± 0:09 1:58 ± 0:02 1:7 ± 0:1 5:3 ± 0:1 23 (0; 0) (2,2) +1:59 ± 0:02 1:31 ± 0:06 1:83 ± 0:04 0:5 ± 0:2 1:7 ± 0:3 4:1 L1228 (0; 0) (1,1) 8:088 ± 0:003 2:71 ± 0:03 0:71 ± 0:01 2:31 ± 0:06 7:0 ± 0:1 14 (0; 0) (2,2) 8:06 ± 0:03 0:49 ± 0:6 0:69 ± 0:06 0:2 ± 0:2 0:6 ± 0:1 0:5 H H L 73 ( 2:8; 7) (1,1) +4:20 ± 0:01 1:66 ± 0:09 0:94 ± 0:03 1:8 ± 0:2 3:5 ± 0:2 9:3 ( 2:8; 7) (2,2) +4:26 ± 0:06 0:31 ± 0:06 0:9 ± 0:1 0:2 ± 0:3 0:4 ± 0:2 0:4 H H L 73 (8:4; 2:8) (1,1) +3:74 ± 0:03 0:7 ± 0:1 0:67 ± 0:07 3:2 ± 0:3 2:1 ± 0:2 3:9 (7; 2:8) (2,2) -» 0:3 k IRAS (1:4; 1:4) (1,1) 4:72 ± 0:02 1:40 ± 0:09 0:56 ± 0:04 1:7 ± 0:4 3:1 ± 0:4 4:8 (1:4; 1:4) (2,2) 4:68 ± 0:06 0:23 ± 0:06 0:6 ± 0:1 0:1 ± 0:1 0:3 ± 0:1 0:2 IRAS l (1:4; 0) (1,1) 3:53 ± 0:01 2:29 ± 0:09 0:69 ± 0:02 1:6 ± 0:2 4:9 ± 0:2 9:3 (1:4; 0) (2,2) 3:58 ± 0:04 0:37 ± 0:06 0:8 ± 0:1 0:1 ± 0:2 0:43 ± 0:04 0:5 L1262 ( 1:4; 0) (1,1) +3:93 ± 0:01 1:86 ± 0:09 0:51 ± 0:02 3:6 ± 0:4 6:6 ± 0:5 9:3 (0; 0) (2,2) -» 0:17 k a Obtained from a multicomponent fit to the magnetic hyperfine structure, using the CLASS package. b Position of the emission peak (offset from the central position given in Table 2.1), where line parameters have been obtained. c Velocity of the line with respect to the local standard of rest. d Main beam brightness temperature of the main line of the transition, obtained from a single Gaussian fit. e Intrinsic line width, obtained taking into account optical depth and hyperfine broadening, but not the spectral resolution of the spectrometer. f Optical depth of the main line. For the (1,1) transition, derived from the relative intensities of the magnetic hyperfine components; for the (2,2) transition, derived from the ratio of the (1,1) and (2,2) antenna temperatures and the optical depth of the (1,1) line, assuming the same excitation temperature for both transitions. g Derived from the transfer equation, where A = f[j(t ex ) J(T bg )] is the amplitude" (Pauls et al. 1983), f is the filling factor, T ex the excitation temperature of the transition, T bg the background radiation temperature and J(T ) the intensity in units of temperature. Note that A ' ft ex, for T ex fl T bg. h Beam-averaged column density for the rotational level (J;K), derived from [N(J;K)=cm 2 ]=C(J;K)[Afi m =K][ V=km s 1 ], with C(1; 1) = 2: and C(2; 2) = 1: (e.g., Ungerechts et al. 1986). i Obtained adopting a 3ff upper limit for the intensity of the satellite lines. j The highest value is obtained with the upper limit of fi m, and the lowest value is obtained assuming optically thin emission. k 3ff upper limit. l See also Table 2.4

75 2.2. Observations 39 Figure 2.2: Same as Fig. 2.1, for the (J, K)=(2,2) inversion transition. Figure 2.3: Spectrum of the H 2 O maser detected near IRAS , towards the position α(1950) = 20 h 18 m 47 ṣ 83, δ(1950) = , as observed in Feb 10, 1990.

76 40 Chapter 2. Ammonia towards molecular and optical outflows observations We observed the (J, K)=(1,1) and the (J, K)=(2,2) inversion transitions of the ammonia molecule using the 37 m radio telescope at Haystack Observatory on January 1993, May 1996 and December At the frequency of these transitions ( GHz and GHz, respectively), the half power beam width of the telescope is 1. 4 and the beam efficiency at an elevation of 40 was 0.41 for the observations made in 1993 and 0.33 for the observations made in 1996 and In all the observing sessions, we used a cooled K-band maser receiver and a channel autocorrelation spectrometer with a full bandwidth of 17.8 MHz. The calibration was made with the standard noise-tube method. All spectra were corrected for elevation-dependent gain variations and for atmosferic attenuation. The rms pointing error of the telescope was 10. Typical system temperatures were 100 K, 140 K and 90 K for the observations made in 1993, 1996 and 1997, respectively. The observations were made in the position switching mode in 1993 and 1997 and in frequency switching mode in During the data reduction the observed spectra were smoothed to a velocity resolution of 0.11 km s 1,achieving a1σ sensitivity of 0.2 K per spectral channel. We have searched for ammonia emision in the 40 regions listed in Table 2.3. In all cases, we first made measurements on a five-point grid centered at the position given in Table 2.3, with a full beam separation between points. The NH 3 (1,1) line was detected in 27 sources. The NH 3 (2,2) line was observed in 15 sources and was detected in 10 of them. The observed spectra of the NH 3 (1,1) and NH 3 (2,2) lines at the position of the emission peak are shown in Figs. 2.4 and 2.5, respectively. In four regions (M N, L1641-S3, HH 270/110 and IRAS ) the maps present two significant emission peaks, whose spectra are also shown in the figures. For V1057 Cyg the emission is very weak, and the spectrum shown corresponds to the average of several positions. In Table 2.4 and 2.5 we give the NH 3 (1,1) and NH 3 (2,2) line parameters obtained from a multicomponent fit to the magnetic hyperfine structure at the position of the emission peak. The intrinsic line widths obtained range from 0.3 kms 1 to 3.6 km s 1 for the NH 3 (1,1) line and from 0.5 kms 1 to 3.8 forthenh 3 (2,2) line. The values of optical depth obtained are in the range for the NH 3 (1,1) and for the NH 3 (2,2) line. Additionally, we have also used a single Gaussian fit to the main line to obtain the main brightness temperature at the position of the

77 2.2. Observations 41 Table 2.3: Regions observed in NH 3 in Region Reference position a Observation Outflow b Ref. Other molecular Ref. D Ref. Alternative names ff(1950) ffi(1950) epoch type observations of the core (pc) of region M N c 00 h 21 m 22 ṣ ffi Jan93 CO M S d 00 h 25 m 59 ṣ ffi Jan93 CO L h 33 m 53 ṣ ffi Jan93 CO 2 HCO +,HCN,CS,NH 3 2,3,4, RNO1B/1C L h 37 m 57 ṣ ffi Jan93 CO 6 HCN,HCO NGC 281 A-W 00 h 49 m 27 ṣ ffi Jan93 CO 7 CS,NH 3,HCN,HCO +,C 18 O,C 34 S 8,9,10, S184 HH h 15 m 34 ṣ ffi Dec97 jet CoKu Tau 1 HH h 23 m 58 ṣ ffi May96 jet, CO 12, DG Tau B HH h 24 m 01 ṣ ffi May96 jet 14 C 18 O, CS 15, DG Tau HH h 25 m 14 ṣ ffi May96 jet, CO? 11,79 CS,C 18 O 17, HH h 28 m 21 ṣ ffi May96 HH L1551 L1551 NE 04 h 28 m 50 ṣ ffi May96 CO, jet 21, L1551 L h 32 m 32 ṣ 0 14 ffi Jan93 CO, HH 23,24 HCO +,C 18 O HH 123 L h 17 m 13 ṣ 8 05 ffi May96, Dec97 CO,H 2,jet 26, HH 240/241,RNO 40 HH h 29 m 52 ṣ 0 06 ffi May96 HH IRAS h 35 m 48 ṣ ffi Jan93 CO 7 HCN,HCO +,CS,NH 3 30, L1641-S3 05 h 37 m 31 ṣ 7 07 ffi Jan93, May96 CO 32 NH 3,CS 33, HH h 39 m 08 ṣ 7 06 ffi May96 HH CB h 44 m 03 ṣ ffi Jan93 CO, jet, H 2 35,36 C 18 O,CS,NH 3,HCN 37,38,39, HH 290 HH 270/ h 48 m 57 ṣ ffi Dec97 jet L1617 IRAS h 49 m 05 ṣ ffi Jan93 CO 7 CS S242 HH h 49 m 09 ṣ ffi Jan93 CO, jet, H 2 44,45,46 CS L1617 HH h 50 m 58 ṣ ffi May96 jet L1617 AFGL h 55 m 20 ṣ ffi May96 CO 7 CS CB h 02 m 06 ṣ 0 16 ffi Jan93 CO 35 C 18 O,CS,HCN 37,38, LBN 1042 L h 28 m 33 ṣ 5 23 ffi May96 CO L h 26 m 32 ṣ 9 15 ffi Jan93 CO 32 C 18 O,NH 3 50, L h 33 m 07 ṣ 6 00 ffi Dec97 CO?, HH 48, HH 108/109 CB h 17 m 57 ṣ ffi Jan93 CO 35 HCN,CS,C 18 O 40,38, L673 e 19 h 18 m 30 ṣ ffi May96 CO 53 NH 3,CS,C 34 S,HCN 54,55, RNO 109 HH h 26 m 37 ṣ ffi May96 jet Parsamyan 21 L h 03 m 45 ṣ ffi Jan93 CO 35 HCN,CS,C 18 O 59,38, CB 216 IRAS h 05 m 02 ṣ ffi May96 CO 60 CS,HCO +,HCN 60,61, V1057 Cyg 20 h 57 m 06 ṣ ffi May96 CO CB h 35 m 14 ṣ ffi Jan93 CO 35 C 18 O,CS 37, B158 IC 1396E 21 h 39 m 10 ṣ ffi Jan93 CO 32 C 18 O,CS,NH 3,HCN,HCO + 64,65,66, GRS 14,IC1396N L h 05 m 09 ṣ ffi Dec97 CO, HH 48, HHL75,HH 354 IRAS h 13 m 24 ṣ ffi May96 CO S134 L h 26 m 37 ṣ ffi May96 CO, HH 69,70 CS,HCO +, HCN,C 18 O HH 363 L1251 e 22 h 37 m 40 ṣ ffi May96 CO, HH 71,72 NH 3,CS,C 18 O 54,55, NGC h 11 m 35 ṣ ffi Jan93 CO 75 HCN,CS,C 34 S 76, a Position where the observations are centered. b CO = Molecular outflow; HH = Isolated Herbig-Haro object; jet = Optical outflow; H 2 = Molecular hidrogen outflow. c See Table 2.1 for H 2O results on source IRAS in this region. d See Table 2.1 for H 2O results on source IRAS in this region. e Additional NH 3 data were obtained in February 1990 (see Table 2.1). References: (1) Yang et al. 1990; (2) Yang et al. 1991; (3) Yang et al. 1995; (4) Estalella et al. 1993; (5) Carpenter, Snell & Schloerb 1990; (6) Yang 1990; (7) Snell et al. 1990; (8) Carpenter et al. 1993; (9) Henning et al. 1994; (10) Cesaroni et al. 1991; (11) Strom et al. 1986; (12) Mundt et al. 1991; (13) Mitchell et al. 1994; (14) Mundt et al. 1987; (15) Hayashi et al. 1994; (16) Ohashi et al. 1991; (17) Ohashi et al. 1996; (18) Onishi et al. 1998; (19) Garnavich et al. 1992; (20) Snell 1981; (21) Moriarty-Schieven et al. 1995; (22) Devine, Reipurth & Bally 1999; (23) Liljeström et al. 1989; (24) Reipurth & Heathcote 1990; (25) Liljeström 1991; (26) Davis et al. 1997; (27) Hoddap & Ladd 1995; (28) Reipurth et al. 1993; (29) Reipurth & Graham 1988; (30) Cesaroni, Felli & Walmsley 1999; (31) Zinchenko et al. 1997; (32) Wilking et al. 1990; (33) Harju et al. 1993; (34) Tatematsu et al. 1993; (35) Yun & Clemens 1994a; (36) Moreira & Yun 1995; (37) Wang et al. 1995; (38) Launhardt et al. 1998; (39) Codella & Scappini 1998; (40) Afonso, Yun & Clemens 1998; (41) Launhardt & Henning 1997; (42) Reipurth et al. 1996; (43) Blitz et al. 1982; (44) Reipurth & Oldberg 1991; (45) Reipurth 1989; (46) Gredel & Reipurth 1993; (47) Yang et al. 1997; (48) Parker et al. 1991; (49) Fukui 1989; (50) Kelly & Macdonald 1996; (51) Kelly & Macdonald 1995; (52) Reipurth & Eiroa 1992; (53) Armstrong & Winnewisser 1989; (54) see Table 3.1; (55) Morata et al. 1997; (56) Sandell, Höglund & Kislyakov 1983; (57) Herbig & Jones 1983; (58) Staude & Neckel 1992; (59) Scappini et al. 1998; (60) Bachiller, Fuente & Tafalla 1995; (61) Gregersen et al. 1997; (62) Wilking et al. 1989; (63) Levreault 1988; (64) Wilking et al. 1993; (65) Serabyn et al. 1993; (66) Weikard et al. 1996; (67) Reipurth et al. 1997; (68) Dobashi et al. 1994; (69) Umemoto et al. 1991; (70) Alten et al. 1997; (71) Sato & Fukui 1989; (72) Eiroa et al. 1994b; (73) Sato et al. 1994; (74) Kun & Prusti 1993; (75) Kameya et al. 1989; (76) Cao et al. 1993; (77) Kameya et al. 1986; (78) Choi, Panis & Evans II 1999; (79) Moriarty-Schieven et al. 1992; (80) Megeath & Wilson 1997

78 42 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.4: Spectra of the (J, K) =(1, 1) inversion transition of the NH 3 molecule towards the positions given in Table 2.4, for the sources detected in the observations. The vertical axis is the main beam brightness temperature and the horizontal axis is the relative velocity with respect to that of the center of the main line (as given in Table 2.4). For some sources, spectra at two different offset positons are shown. The spectrum of V1057 Cyg corresponds to the average of positions with detected emission in a five-point map.

79 2.2. Observations 43 Figure 2.4: Continued

80 44 Chapter 2. Ammonia towards molecular and optical outflows Table 2.4: NH 3 (1,1) line parameters of sources observed in Region Position a b V LSR T MB (m) c V d e fi m f Afi m N(1; 1) g (arcmin) (km s 1 ) (K) (km s 1 ) (K) (10 13 cm 2 ) M N (2:8; 1:4) 18:78 ± 0:02 0:89± 0:07 0:90 ± 0:05 1:7 ± 0:3 1:9 ± 0: (0; 0) 20:23 ± 0:01 0:65 ± 0:04 1:18 ± 0:04 1:0 ± 0:1 1:06 ± 0: M S (0; 0) 17:41 ± 0:02 0:57 ± 0:05 1:10 ± 0:05 0:8 ± 0:2 0:83 ± 0: L1287 (0; 0) 17:63 ± 0:05 2:51 ± 0:05 1:77 ± 0:01 0:90 ± 0:03 3:80 ± 0: L1293 (0; 0) 17:67 ± 0:01 1:06± 0:05 0:79 ± 0:03 0:7 ± 0:2 1:7 ± 0: NGC 281 A-W (0; 0) 30:32 ± 0:04 0:54 ± 0:07 2:2 ± 0:1 1:3 ± 0:3 0:93 ± 0: HH 156 (0,0) -» 0: HH 159 (0,0) -» 0: HH 158 (0,0) -» 0: HH 31 ( 7; 0) +6:86 ± 0:01 2:2 ± 0:1 0:42 ± 0:01 2:6 ± 0:2 6:7 ± 0: HH265 ( 1:4; 1:4) +6:68 ± 0:01 1:9 ± 0:1 0:40 ± 0:02 2:5 ± 0:3 5:7 ± 0: L1551 NE (0; 0) +6:64 ± 0:02 0:79 ± 0:09 0:47 ± 0:03 5:0 ± 0:8 3:5 ± 0: L1642 (0; 0) -» 0: L1634 (1:4; 0) +8:00 ± 0:01 1:4 ± 0:1 0:81 ± 0:04 0:6 ± 0:2 2:0 ± 0: HH 59 (0; 0) -» 0: IRAS (0; 0) 16:89 ± 0:01 1:44 ± 0:05 2:32 ± 0:03 0:67 ± 0:07 1:95 ± 0: L1641-S3 (0; 0) +4:96 ± 0:01 2:0 ± 0:1 0:68 ± 0:04 1:3 ± 0:3 3:9 ± 0: ( 2:8; 0) +3:76 ± 0:01 1:8 ± 0:2 0:30 ± 0:02 3:3 ± 0:5 7:0 ± 0: HH 68 (0; 0) -» 0: CB 34 (0; 0) +0:72 ± 0:02 0:77 ± 0:06 1:37 ± 0:06 0:4 ± 0:2 0:99 ± 0: HH 270/110 (0; 0) +8:86 ± 0:02 0:67 ± 0:06 0:65 ± 0:04 1:3 ± 0:3 1:3 ± 0: ( 2:8; 0) +8:70 ± 0:03 0:8 ± 0:1 0:8 ± 0:1 0:4 ± 0:5 1:1 ± 0: IRAS (0; 0) +0:78 ± 0:03 0:41 ± 0:05 1:5 ± 0:1 0:1 ± 0:4 0:45 ± 0: HH 111 (0; 0) +8:72 ± 0:02 0:56 ± 0:06 0:78 ± 0:08 0:4 ± 0:3 0:7 ± 0: HH 113 (0; 0) -» 0: AFGL 5173 (0; 0) -» 0: CB 54 (0; 0) +19:55 ± 0:01 0:73 ± 0:04 1:14 ± 0:04 0:8 ± 0:2 1:11 ± 0: L1709 (0; 0) -» 0: L379 (0; 0) +18:89 ± 0:01 2:87 ± 0:05 2:84 ± 0:02 1:86 ± 0:03 5:98 ± 0: L588 (0; 0) +10:86 ± 0:02 1:3 ± 0:1 0:58 ± 0:04 2:4 ± 0:4 3:5 ± 0: CB 188 (0; 0) -» 0: L673 k (0; 1:4) +7:11 ± 0:01 2:5 ± 0:1 0:41 ± 0:1 2:5 ± 0:3 7:5 ± 0: HH221 (0; 0) -» 0: L797 (0; 0) -» 0: IRAS (0; 1:4) +6:86 ± 0:02 1:7 ± 0:2 0:93 ± 0:04 3:4 ± 0:3 5:6 ± 0: ( 1:4; 1:4) +5:06 ± 0:02 1:8 ± 0:2 0:96 ± 0:04 0:8 ± 0:2 2:6 ± 0: V1057 Cyg h (0; 0) +4:30 ± 0:04 0:3 ± 0:1 0:58 ± 0:09» 3 i 0:3 0:7 j CB 232 (0; 0) +12:32 ± 0:02 0:58 ± 0:05 0:68 ± 0:04 1:8 ± 0:3 1:3 ± 0: IC 1396E (0; 0) +0:53 ± 0:02 0:86 ± 0:05 1:89 ± 0:04 0:8 ± 0:1 1:22 ± 0: L1165 (0; 0) 1:64 ± 0:04 0:35 ± 0:08 0:6 ± 0:1 3 ± 1 0:9 ± 0:

81 2.2. Observations 45 Table 2.4: Continued Region Position a b V LSR T MB (m) c V d e fi m f Afi m N(1; 1) g (arcmin) (km s 1 ) (K) (km s 1 ) (K) (10 13 cm 2 ) IRAS (0; 0) 18:62 ± 0:04 0:55 ± 0:09 1:2 ± 0:1 0:4 ± 0:4 0:7 ± 0: L1221 (0; 0) 4:36 ± 0:01 2:5 ± 0:1 0:71 ± 0:01 2:1 ± 0:1 6:1 ± 0: L1251 k (0; 0) -» 0: NGC 7538 (0; 1:4) 56:22 ± 0:02 1:9 ± 0:1 3:57 ± 0:05 0:35 ± 0:06 2:32 ± 0: a Position of the emission peak, where line parameters have been obtained (in offsets from the position given in Table 2.3). b Velocity ofthe line peak with respect to the local standard of rest. c Main beam brightness temperature of the main line of the transition, obtained from a single Gaussian fit. For undetected sources a 3ff upper limit is given. d Intrinsic line width, obtained taking into account optical depth and hyperfine broadening, but not the spectral resolution of the spectrometer. e Optical depth of the main line derived from the relative intensities of the magnetic hyperfine components. f Derived from the the transfer equation, where A = f[j(t ex ) J(T bg )] is the amplitude" (Pauls et al.1983), f is the filling factor, T ex is the excitation temperature of the transition, T bg is the background radiation temperature and J(T ) is the intensity in units of temperature. Note that A ' ft ex,fort ex fl T bg. g Beam-averaged column density for the rotational level (1; 1). Upper limit is obtained from " N(1; 1) cm 2 # =1: e1:14=tex» +1 e 1:14=Tex 1 fi V m km s 1 where T ex is derived from the transfer equation assuming a filling factor f =1. If T ex fl T bg the beam averaged column density is proportional to the amplitude" A, and the explicit dependence on T ex disappears, reducing to " #» N(1; 1) =2: Afi m cm 2 providing the lower limit for the beam-averaged column density. K» V km s 1 h Line parameters have been obtained by averaging several positions of afive-point map. i Obtained adopting a 3ff upper limit for the intensity of the satellite lines. j The highest value is obtained from the upper limit of fi m and the lowest value is obtained assuming optically thin emission. k See also Table 2.2. ; ;

82 46 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.5: Same as Fig. 2.4, for the (J, K) = (2,2) inversion transition towards the positions given in Table 2.5 emission peak. The values obtained for the main beam brightness temperature for the detected sources range from 0.3 Kto 3K. Additionally, we searched for the H 2 O maser line (at the frequency of GHz) towards the six sources listed in Table 2.6. The H 2 Oobservations were carried out on May 16 and 17, 1996 with the same spectrometer and bandwidth used for the NH 3 observations. We reached a typical sensitivity of 1 Jy (1σ) for spectral channel. From the six sources observed in H 2 O, we have only detected significant (> 3σ) H 2 O emission in two of them, HH 265 and AFGL The spectra of these H 2 O maser are shown in Fig In Table 2.6 we listed the line parameters obtained for the detected H 2 O masers from a Gaussian fit at the position

83 2.3. Results 47 Table 2.5: NH 3 (2,2) line parameters of sources observed in Region Position a b V LSR T MB (m) c V d e fi m f Afi m N(2; 2) g (arcmin) (km s 1 ) (K) (km s 1 ) (K) (10 13 cm 2 ) M N (2:8; 1:4) 18:4 ± 0:1 0:15 ± 0:06 0:9 ± 0:2 0:2 ± 0:1 0:17 ± 0: (0; 0) -» 0: L1287 (0; 0) 17:57 ± 0:02 0:98 ± 0:05 1:93 ± 0:04 0:27 ± 0:04 1:13 ± 0: L1293 (0; 0) -» 0: HH 31 ( 7; 0) 6:94 ± 0:04 0:24 ± 0:06 0:51 ± 0: :27 ± 0: HH 265 ( 1:4; 1:4) -» 0: IRAS (0; 0) 16:79 ± 0:04 0:7 ± 0:1 2:6 ± 0:1 0:28 ± 0:05 0:83 ± 0: L1641-S3 (0; 0) +5:1 ± 0:1 0:3 ± 0:1 1:2 ± 0:1 0:1 ± 0:1 0:30 ± 0: CB 34 (0; 0) -» 0: CB 54 (0; 0) -» 0: L379 (0; 0) +18:80 ± 0:02 1:3 ± 0:1 3:45 ± 0:05 0:53 ± 0:02 1:7 ± 0: IRAS (0; 0) +6:46 ± 0:05 0:7 ± 0:1 1:9 ± 0:1 0:5 ± 0:1 0:93 ± 0: CB 232 (0; 0) -» 0: IC 1396E (0; 0) +0:42 ± 0:06 0:33 ± 0:06 2:4 ± 0:2 0:23 ± 0:06 0:37 ± 0: L1221 (0; 0) 4:49 ± 0:03 0:5 ± 0:1 1:0 ± 0:1 0:19 ± 0:03 0:55 ± 0: NGC 7538 (0; 0) 56:91 ± 0:03 0:76 ± 0:05 3:8 ± 0:1 0:13 ± 0:07 0:81 ± 0: a d;f See footnotes of Table 2.4. e Optical depth of the (2,2) main line derived from the ratio of the (1,1) to (2,2) antenna temperatures and the optical depth of the (1,1) line, assuming the same excitation temperature for both transitions. g Beam-averaged column density for the rotational level (2,2). Upper limit is derived from " N(2; 2) cm 2 #» =7: e1:14=tex +1 e 1:14=Tex 1 fi V m km s 1 assuming that both filling factor and excitation temperature are the same for the (1,1) and (2,2) transitions. If T ex fl T bg,thebeamaveraged column density is proportional to the amplitude" A, and the explicit dependence ; on T ex disappears, reducing to " #» N(2; 2) =1: Afi m cm 2 K providing the lower limit for the beam-averaged column density.» V km s 1 ; giveninthetable. 2.3 Results In Table 2.7 we list the physical parameters of the molecular condensations, derived from the NH 3 data given in Tables 2.2, 2.4 and 2.5, following the procedures explained in the footnotes of Table 2.7. We have mapped the NH 3 (1,1) emission in all the detected regions, except V1057Cyg and L1551NE. Maps are shown in Figs. 2.7, 2.9 to 2.21, 2.23 to 2.36,

84 48 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.6: Spectra of the H 2 O masers detected in May 16, 1996, in the regions HH 265 (bottom) and AFGL 5173 (top) at the positions given in Table to 2.39, 2.41 to 2.48, 2.51 and We have not mapped the region V1057 Cyg because the emission is too weak in all positions. The spectrum of this region shown in Fig. 2.4 and physical parameters listed in Table 2.7 have been obtained by adding several points of a five-point map. In L1551NE, we have detected intense NH 3 emission in four positions, however we have not been able to map the region (see 2.3.8). A summary of the relevant information, taken from literature, about the sources associated with these regions is listed in Table M North This region is associated with a bipolar molecular outflow (Yang et al. 1990) and contains several low-luminosity objects. Two of these objects, IRAS and IRAS , fall inside the outflow lobes, being IRAS the proposed driving source of the molecular outflow (Yang et al. 1990). We have observed in ammonia the region around both IRAS sources.

85 2.3. Results 49 Figure 2.7: Contour map of the peak antenna temperature of the main line of the ammonia (J,K)=(1,1) inversion transition (thick line) in the M N. The lowest contour level is 0.3 K, and the increment is 0.01 K. The observed positions are indicated with small crosses. The half power beam width of the telescope is shown as a circle. The positions of several relevant objects in the region are indicated. The CO bipolar outflow is from Yang et al. (1990)(solid contours indicate blueshifted gas, and dashed contours indicate redshifted gas) The NH 3 structure (Fig. 2.7) consists on two subcondensations, each one peaking very close to the position of an IRAS source. This result suggests that both IRAS sources are embedded in the high density gas. Our results show that the velocity is different for each clump (see Table 2.4 and Fig. 2.8). The observed difference in velocity is consistent with a gravitationally bound rotational motion of the two clumps. On the basis of the geometrical position of IRAS , close to the emission peak of the blueshifted gas, and its cold IR color, Yang et al. (1990) favour this source as the driving source of the outflow. The association of this source with an ammonia emission maximum supports its identification as the outflow driving

86 50 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.8: Position-velocity diagram of the NH 3 (1,1) main line along an axis passing towards the two maxima (P.A. 45 ) of the M North condensation. The lowest contour level is 0.3 K and the increment is 0.05 K. source. However, we note that IRAS falls very close to the position of an ammonia emission peak, it lies close to the emission peak of the redshifted gas and its IRAS colors are characteristic of an embedded source (although the source appears confused in the 60 and 100 μmiras bands). Therefore, based on these results, both IRAS sources are valid candidates for the outflow excitation. The radio continuum sources detected in the region (Anglada et al. 2001) fall outside the ammonia condensation (see Fig. 2.7), therefore they appear to be unrelated to the star-forming region M South This region is associated with several IRAS sources and with a CO bipolar outflow (Yang et al. 1990). The outflow is asymmetric, with the red lobe more intense than the blue one. Two sources, IRAS and IRAS , lie inside the outflow lobes. Yang et al. proposed IRAS as the driving source of the

87 2.3. Results 51 Figure 2.9: Same as Fig. 2.7, for the M South region. The NH 3 lowest contour is 0.2 K and the increment is 0.1 K. The map of the CO bipolar outflow is from Yang et al. (1990) (solid countours indicate redshifted gas, and dashed contours indicate blueshifted gas). outflow. We have observed in ammonia the region around both sources. The NH 3 condensation (Fig. 2.9) shows an structure elongated in the NW-SE direction. Both IRAS and IRAS are located close to the ammonia emission maximum, suggesting that they are embedded sources. Both sources have similar IRAS colors, but appear confused at 60 and 100 μm. Therefore, we cannot favor one of them as the driving source of the outflow. A cm radio continuum source is detected at the edge of the ammonia condensation (Anglada et al. 2001). Unfortunately, the information available for this source is not enough to infer the nature of the emission.

88 52 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.10: Same as Fig. 2.7, for the L1287 region. The NH 3 lowest contour is 0.3 K and the increment is 0.2 K. The map of the CO bipolar outflow is from Snell et al. (1990) L1287 The dark cloud L1287 is associated with an energetic bipolar molecular outflow (Snell et al. 1990, Yang et al. 1991). At the center of the outflow lies the source IRAS , that has been proposed as the outflow exciting source (Yang et al. 1990). The brightest visible object in the region, RNO 1 (Cohen 1980), lies 40 NE of the nominal IRAS position. However, because of the low angular resolution of the IRAS data, several young stellar objects fall inside the IRAS error ellipsoid. Two of them, the source RNO 1C (one component of the FU Ori binary sistem RNO 1B/1C), and a centimeter radio continuum source, VLA 3, (which lies at the center of symmetry of the polarization pattern; Weintraub & Kastner 1993) are proposed as the exciting source of the outflow by Kenyon et al. (1993) and Anglada

89 2.3. Results 53 et al. (1994), respectively. These objects appear at different evolutive stages, and at present, it is unsettled which one of these objects is the true outflow exciting source. The region was observed in HCN, HCO + (Yang et al. 1991), CS (Yang et al. 1995; McMuldroch et al. 1995) and in NH 3 (Estalella et al. 1993). Estalella et al. (1993) found a gradient in the NW-SE direction, that was interpreted as due to a rotating core. The condensation we have mapped (Fig. 2.10) is clearly elongated in the northwestsoutheast direction, perpendicular to the CO outflow axis, in good agreement with the results of Estalella et al. (1993). The ammonia emission peaks near the position of IRAS , RNO 1B/1C and VLA 3. However, due to the small projected angular separation between all these objects ( 5 10 ), we can not establish from our data which of these sources is the best candidate for exciting the outflow in terms of its proximity to the ammonia emission peak (see, Chapter 4 for details of high angular resolution ammonia observations). We have found a velocity gradient of 1.23 km s 1 pc 1 in the NW-SE direction, in good agreement with the results obtained by Estalella et al. (1993) L1293 Yang (1990) discovered a bipolar molecular outflow in this region and proposed IRAS as its driving source. The NH 3 structure presents two emission maxima separated by 4 (Fig. 2.11). The strongest ammonia peak coincides with the position of IRAS This IRAS source is not detected at 12 μm and its infrared flux increases steeply towards longer wavelenghts. These IR results, along with its association with strong NH 3 emission and with an H 2 O maser (Wouterloot et al. 1993), suggest that IRAS is a young stellar object, deeply embedded in the high density gas, and the most plausible exciting source of the outflow. The ammonia emission extends to the SE of the IRAS source, reaching a secondary, weaker emission maximum with no known associated object. The HCN, HCO + and 13 CO emission also peak towards the IRAS position (Yang 1990), in agreement with our ammonia results.

90 54 Chapter 2. Ammonia towards molecular and optical outflows Table 2.6: H 2 O maser emission observed in May 1996 and line parameters a Region Position b V LSR c S ν d ΔV e (arcmin) (km s 1 ) (Jy) (kms 1 ) M N (2.8,1.4) HH 265 (0,0) 9.13 ± ± ± 0.2 (0,0) 7.14 ± ± ± 0.2 L1634 (1.4,0) L1641-S3 (0,0) AFGL 5173 f (0,0) ± ± ± 0.06 L1221 (0,0) a Obtained from a Gaussian fit to the line profile. b Position of the emission peak, where line parameters have been obtained (in offsets from the position given in Table 2.3). c Velocity of the line peak with respect to the local standard of rest. d Flux density of the line peak. For undetected sources a 3σ upper limit is given. e Full width at half maximum. f Maser located at the position of IRAS , that could be responsible for the maser emission. However, we have not detected any significant NH 3 emission towards this source (see Table 2.4). Brand et al. (1994) detected highly variable H 2 O emission towards this source between March 1989 and January The velocity of the emission peak ranges from -7.6 to 13.1 km s 1, while we do not detect significant H 2 O emission outside the velocity range 6.5 <V LSR < 7.2 kms 1.

91 2.3. Results 55 Table 2.7: Physical parameters of the mapped NH 3 condensations Region Size a b T rot N(H 2 ) c M d e M vir n(h 2 ) f (arcmin) (pc) (K) (10 22 cm 2 ) (M fi ) (M fi ) (10 3 cm 3 ) M N (2. 0 8; ) 3:9 2:7 0:96 0: :7 6: M N (0; 0) 3:0 2:0 0:75 0:50» 15 0: ο 2.6 M S 3:7 2:4 0:91 0:59 ο 13:5 0:7 2: ο 2.8 L1287 3:8 1:9 0:93 0: :6 7: L1293 2:7 2:0 1:26 0:94» 13 1: ο 7.7 NGC 281 A-W 1:9 1:6 1:88 1:62 ο 20 1:3 6: ο 1.3 HH31 2:8 2:0 0:11 0: :7 7: HH265 4:2 2:3 0:20 0:11» 9 3:3 9 2 ο 11.3 L1551 NE 1:4 1:4 0:07 0:07 ο 25 1:0 5: ο 1.1 L1634 2:6 2:1 0:34 0:28 ο 12 1:6 2: ο 13.1 RNO 43 2:6 1:5 0:30 0:18 ο 15 ο 0:4 ο 3 10 ο 1.6 HH 83 > ο 2:5 2:3 > ο 0:34 0:31 ο > ο 5 > ο 6 > ο 1.5 HH 84 > ο 2:6 2:5 > ο 0:36 0:34 ο > ο 8 > ο 66 > ο 0.5 HH 86/87/88 2:4 1:9 0:33 0:26 ο 19 ο 0:3 ο 4 16 ο 24.0 L1641-N 2:3 4:5 0:32 0:63 ο 23 ο 3:5 ο ο 5.9 IRAS :1 1:9 1:60 0: :9 5: L1641-S3 (V ο 4:9 km/s) 3:8 2:2 0:53 0:31 12:6 2:4 4: L1641-S3 (V ο 3:8 km/s) 5:8 2:8 0:81 0:39» 13:5 1: CB 34 2:0 1:7 0:89 0:76» 12 1: ο 7.8 HH 270/110 (0; 0) 1:4 1:6 0:19 0:21 ο 13:6 0:7 2: ο 2.5 HH270/110 ( ; 0) 2:8 1:7 0:37 0:23 ο 13:6 0:8 1: ο 10.0 IRAS :6 1:7 1:59 1:05 ο 15:5 0:5 0: ο 14.3 HH 111 1:6 1:8 0:22 0:23 ο 13 0:5 1: ο 5.6 CB 54 1:7 1:6 0:74 0:68» 15 1: ο 3.3 L100 > ο 2:3 2:4 > ο 0:15 0:16 ο > ο 1 > ο 3 > ο 1.1 L483 2:0 1:8 0:12 0: L379 2:0 2:0 1:16 1: :4 21: L588 4:1 1:9 0:37 0:17 ο 8 4:1 11: ο 7.5 L673(NW) g 4:7 2:0 0:41 0:18» 12 2: L673(SE) h 2:2 2:0 0:19 0:17» 12 2: ο 10.9 IRAS (0; ) 3:1 2:0 0:63 0:41 16:8 3:6 9: IRAS ( ; ) 3:0 2:0 0:61 0:41 16:8 1:8 3: IRAS :7 2:0» 1:99 2: » 3200» V1057 Cyg 1:4 1:4 0:29 0:29 ο 10 0:2 6: :3 0.7 L1228 2:9 1:9 0:25 0: CB 232 2:6 2:5 0:45 0:43» 11 0: ο 2.2 IC 1396E 3:2 1:9 0:70 0: :4 3: HHL 73 ( 2:8; 7) 2:7 2:0 0:71 0: HHL 73 (8:4; 2:8) 3:1 2:4 0:81 0:63» 19 0: L1165 3:5 2:3 0:76 0:49 ο 9 0:9 7: ο 1.3 IRAS :1 2:3 0:81 0:59 ο 15:8 0:6 1: ο 4.1

92 c Beam-averaged H 2 column density, obtained from the NH 3 column density adopting an NH 3 56 Chapter 2. Ammonia towards molecular and optical outflows Table 2.7: Continued Region Size a T rot b N(H 2 ) c M d M vir e n(h 2 ) f (arcmin) (pc) (K) (10 22 cm 2 ) (Mfi) (Mfi) (10 3 cm 3 ) L1221 2:1 2:0 0:12 0: :9 7: IRAS :3 2:0 0:29 0: IRAS :0 1:8 0:61 0: NGC :5 2:4 1:96 1: :3 7: L1262 2:8 1:7 0:16 0:10» 9 4: a Major and minor axes of the half-power contour of the NH 3 emission. For sources L1551 NE and V1057 Cyg a size equal to the beam size has been assumed. b Rotational temperature, derived from the ratio of NH 3 column density of the (1,1) and (2,2) levels for the sources where the (2,2) line was detected. For the sources undetected in the (2,2) line, an upper limit is obtained assuming optically thin emission. For sources not observed in the (2,2) line, it is assumed that T ex (CO) = T k = T rot (22 11), where the CO data are from Yang et al (M S), Henning et al (NGC 281 A-W), Moriarty-Schieven et al (L1551 NE), Cabrit et al (RNO 43), Bally et al (HH 83), Morgan & Bally 1991 (HH 84), Maddalena et al (HH 86/87/88), Morgan et al (L1641-N), Reipurth & Oldberg 1991 (HH 270/110 and HH 111), Snell et al (IRAS 05490), Parker et al (L100), Parker et al (L588 and L1165), Levreault 1988 (V1057 Cyg) and Dobashi et al (IRAS 22134). For L1634, a T rot =12 K has been assumed. abundance of [NH 3 /H 2 ]=10 8 (see Anglada et al for a discussion on NH 3 abundances). The NH 3 column density is obtained assuming that only the rotational metastable levels of the NH 3 are significantly populated at their LTE ratios corresponding to T k = T R (22 11). d Mass of the condensation, derived from the beam-averaged H 2 column density and the observed area. e Virial mass obtained from [M vir /Mfi]=210[R/pc][ V /km s 1 ] 2, where R is the radius of the clump, taken as half the geometrical mean of the two linear sizes, and V is the intrinsic line width given in Table 2.2 and 2.4. f Volume density, derived from the two-level model (Ho &Townes 1983). g Parameters of the northwestern clump. h Parameters of the southeastern clump.

93 2.3. Results 57 Table 2.8: Summary of properties of relevant sources in the mapped regions Region IRAS L bol Ref. Evolutionary Ref. Detection at Ref. H2O Ref. Outflow Ref. (Lfi) status other wavelenghts maser? source? M N Yes 2 Yes ? 3 M S No 4 Yes ? 3 L Class I? a 6 NIR,smm,mm,cm 7,5,8,9 Yes 6? 15 L < Yes 11 Yes 10 NGC 281 A-W a - NIR,FIR,mm 7,13,12 Yes 14 Yes 15 HH Class I 16 NIR,FIR,smm,mm 16,17,18,19 No 11 Yes 20 L1551 NE Class 0 22 NIR,smm,mm,cm 23,18,19, Yes 22 L Class 0 92 NIR,FIR,smm,mm,cm 26,17,27,23,92 No 28 Yes 26 IRS 7 b 0:03 c 92 Class I/0 92 NIR,smm 26, Yes 26 RNO Class I 96 smm,mm,cm, 99,25,97 No 80 Yes 98 HH NIR,smm,mm,cm 101,27,25, Yes 102 L1641-N Class I 21 NIR,sm,mm,cm 30,103,21,9 Yes 105 Yes Class I 106 NIR,sm,cm 30,103,9 - -? 107 IRAS Herbig Ae/Be? a 129 NIR 116,129 Yes 75 Yes 15 L1641-S Class I 31 NIR,FIR,smm,mm,cm 31,32,27,30,33, Yes 34 Yes 35 CB Class I 37 NIR,smm,mm,cm 37,38,36,39 No 11 Yes 40 HH 270/ Class I 42 NIR,FIR,cm 43,42,44 No 45 Yes Class I 46 NIR,cm 46, Yes 47 IRAS Class I? a 7 NIR,FIR,cm 7,13 No 14 Yes 15 HH Class 0 48 NIR,smm,mm,cm 49,25,50,51 No 28 Yes 42 CB Class I 36 NIR,smm,mm,cm 52,37,38,53 No 54 Yes 40 L < ο NIR 109 No 54 Yes 108 L Class0/I 117 FIR,smm,mm,cm 110,111,127,112 Yes 105 Yes 81 L a smm,mm,cm 55,5 Yes 56 Yes 35 L Class I 57 mm ? 57 L ? No 28 Yes No No 93 IRAS Class 0 59 NIR,FIR,mm,cm 60,61,62,63 Yes 64 Yes d NIR,cm 60,63 - -? - IRAS < ο a - NIR,smm,mm 116,5 Yes 114 Yes 115 V1057 Cyg FU Or 65 NIR,IR,FIR,cm,mm,smm 66,67,68,69 Yes 70 Yes 77 L NIR,mm,cm 118,119,104 No 28 Yes 120 CB Class I 37 NIR,mm,smm 37,36, Yes 40 IC 1396E Class 0 72 NIR,FIR,mm,smm 73,74,72 Yes 75 Yes 35 HHL Yes Yes 121 Yes < Yes 122 L Class I/FU Or 78 NIR 78,79 No 80 Yes 81,82 IRAS Class I 83 FIR Yes 83 L TTau? No 91 Yes 84 L Class I/II 125 NIR,smm,mm,cm 125,27,104 Yes 105 Yes Class I 128 cm 104 Yes 126 Yes 124 NGC 7538 IRS 1-3 b ο a - NIR,FIR,mm 85,89 Yes 86,88 Yes 87 IRS 9 b ο a - NIR,FIR,mm 85 Yes 88 Yes 87 IRS 11 b a - FIR,mm,smm 85,90 Yes 88 Yes 87 L Class I 128 mm,cm 127,104 No 28 Yes 81 a Probable young massive star/stars. b NIR source. No IRAS source at this position. c Submillimeter luminosity. d IRAS luminosity. References:(1) Yang et al. 1990; (2) Han et al. 1998; (3) this work; (4) see Table 2.1; (5) McCutcheon et al. 1995; (6) Fiebig 1997; (7) Carpenter et al. 1993; (8) McMuldroch et al. 1995; (9) Anglada et al. 1994; (10) Yang 1990; (11) Wouterloot et al. 1993; (12) Henning et al. 1994; (13) Carpenter, Snell & Schloerb 1990; (14) Henning et al. 1992; (15) Snell et al. 1990; (16) Gómez et al. 1997; (17) Cohen et al. 1985; (18) Padgett et al. 1999; (19) Moriarty-Schieven et al. 1994; (20) Strom et al. 1986; (21) Chen et al. 1995; (22) Devine, Reipurth & Bally 1999; (23) Hoddap & Ladd 1995; (24) Rodr guez, Anglada & Raga 1995; (25) Reipurth et al. 1993; (26) Davis et al. 1997; (27) Dent et al. 1998; (28) Felli, Palagi & Tofani 1992; (29) Cesaroni, Felli & Walmsley 1999; (30) Zavagno et al. 1997; (31) Chen & Tokunaga 1994; (32) Price, Murdock & Shivanandan 1983; (33) Morgan et al. 1990; (34) Wouterloot & Walmsley 1986; (35) Wilking et al. 1990; (36) Launhardt & Henning 1997; (37) Yun & Clemens 1995; (38) Launhardt, Ward-Thompson & Henning 1997; (39) Yun et al. 1996; (40) Yun & Clemens 1994a; (41) Moreira & Yun 1995; (42) Reipurth & Olberg 1991; (43) Garnavich et al. 1997; (44) Rodr guez et al. 1998; (45) Palla et al. 1993; (46) Reipurth, Raga & Heathcote 1996; (47) Reipurth et al. 1996; (48) Cernicharo, Neri & Reipurth 1997; (49) Gredel & Reipurth 1993; (50) Stapelfeldt & Scoville 1993; (51) Rodr guez & Reipurth 1994; (52) Yun & Clemens 1994b; (53) Moreira et al. 1997; (54) Codella et al. 1995; (55) Kelly & Macdonald 1996; (56) Codella, Felli & Natale 1996; (57) Chini et al. 1997; (58) Gregersen et al. 1997; (59) Bachiller, Fuente & Tafalla 1995; (60) Chen et al. 1997; (61) Di Francesco et al. 1998; (62) Choi, Panis & Evans II 1999; (63) Anglada, Rodr guez & Torrelles 1998a; (64) Brand et al. 1994; (65) Herbig 1977; (66) Greene & Lada 1977; (67) Kenyon & Hartmann 1991; (68) Rodr guez & Hartmann 1992; (69) Weintraub, Sandell & Duncan 1991; (70) Rodr guez et al. 1987; (71) Huard et al. 1999; (72) Sugitani et al. 2000; (73) Wilking et al. 1993; (74) Saraceno et al. 1996; (75) Tofani et al. 1995; (76) Kenyon 1999; (77) Evans II et al. 1994; (78) Reipurth & Aspin 1997; (79) Tapia et al. 1997; (80) Persi, Palagi & Felli 1994; (81) Parker et al. 1991; (82) Reipurth et al. 1997; (83) Dobashi et al. 1994; (84) Umemoto et al. 1991; (85) Werner et al. 1979; (86) Genzel &Downes 1977; (87) Kameya et al. 1989; (88) Kameya et al. 1990; (89) Akabane et al. 1992; (90) Minchin & Murray 1994; (91) Claussen et al. 1996; (92) Beltrán et al. 2001b; (93) Armstrong & Winnerwisser 1989; (94) Larionov et al. 1999; (95) Moorkerja et al. 1999; (96) André 1996; (97) Anglada et al. 1992; (98) Edwards & Snell 1984; (99) Zinnecker et al. 1992; (100) Rodr guez & Reipurth 1998; (101) Moneti & Reipurth 1995; (102) Bally et al. 1994; (103) Chen et al. 1993; (104) Anglada et al. 1998b; (105) Xiang &Turner 1995; (106) Strom et al. 1989a; (107) Morgan et al. 1991; (108) Parker et al. 1988; (109) Reipurth & Gee 1986; (110) Ladd et al. 1991a; (111) Fuller et al. 1995; (112) Beltrán et al. 2001a; (113) Odenwald & Schwartz 1993; (114) Palla et al. 1991; (115) Little et al. 1988; (116) Yao et al. 2000; (117) Tafalla et al. 2000; (118) Magnier et al. 1999; (119) Osterloh & Beckwith 1995; (120) Haikala & Laureijs 1989; (121) Gyulbudaghian et al. 1987; (122) Dobashi et al. 1993; (123) Dobashi et al. 1992; (124) Sato et al. 1994; (125) Rosvick&Davidge 1995; (126) Toth & Kun 1997; (127) Motte & Andre 2001; (128) Parker 1991; (129) Porras et al. 2000

94 58 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.11: Same as Fig. 2.7, for the L1293 region. The NH 3 lowest contour level is 0.2 K, and the increment is 0.1 K NGC 281 A-West This region is associated with a bipolar molecular outflow proposed to be driven by the luminous source IRAS (Snell et al. 1990; Henning et al. 1994). A near-ir cluster (Carpenter et al. 1993) and several H 2 O maser spots are found in association with the IRAS source (Henning et al. 1992). Henning et al. (1994) modeled the observed spectral energy distribution from 10 μmto 1 mm, concluding that the IRAS source is a very good candidate for a deeply embedded and very young protostellar object.

95 2.3. Results 59 We have detected an ammonia clump (Fig. 2.12) which appears unresolved with our beam. The NH 3 emission peaks at the position of IRAS Our results are in agreement with the 40 NH 3 map of Henning et al. (1994) that reveal that the ammonia clump is elongated along the east-west direction with the emission peak towards the position of the IRAS source. CS emission mapped by Carpenter et al. (1993) with an angular resolution of 50 also peaks towards the position of the IRAS source. These results, along with the spectral energy distribution of the source suggest that IRAS is a very young object deeply embedded in the high density gas and that it is the most likely candidate to excite the outflow. Our ammonia results suggest that there is not a significant amount of dense gas in association with the source IRAS , located 2 to the west of IRAS HH 31 The HH 31 jet is a sinusoidal chain of knots having a linear extent of 0.2 pc(herbig 1974; Gómez et al. 1997). Cohen & Schwartz (1983) found four near-infrared sources (IRS1, IRS2, IRS3 and IRS4) in the vicinity of the jet, being IRS 2, that coincides with IRAS , the proposed exciting source of the jet. This source has been detected at millimeter and sub-millimeter wavelengths (Moriarty-Schieven et al. 1994) and apparently drives a small molecular outflow (Moriarty-Schieven et al. 1992), although no map has been published. In the near-infrared images, IRAS appears as a bipolar reflection nebula (Padgget et al. 1999). We have searched for ammonia emission towards the four near-infrared sources. The ammonia condensation (Fig. 2.13) is elongated in the NE-SW direction, and it is in good agreement with the NH 3 map shown by Benson & Myers (1989). The sources HH 31 IRS2 and IRS1 lie at the edge of the condensation and we have not detected significant emission towards IRS3 and IRS4, which lie far away (more than 8 arcmin) from the condensation. The NH 3 emission peak is displaced 3 ( 0.14 pc) to the SW of the HH 31 IRS2 position. To our knowledge, no source has been reported towards the position of the NH 3 emission peak. We suggest that high sensitivity observations could reveal a deeply embedded object at this position.

96 60 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.12: Same as Fig. 2.7, for the NGC 281 A West region. The NH 3 lowest contour level is 0.15 K, and the increment is K. The CO bipolar outflow is from Snell et al. (1990) (solid contours indicate redshifted gas, and dashed contours indicate blueshifted gas) HH 265 HH 265 is an isolated Herbig-Haro object, located in the L1551 cloud, whose exciting source remains unknown. We have discovered an H 2 O maser (see Fig. 2.6) towards the position of the HH object. The maser shows two velocity components, whose line parameters are given in Table 2.6. The H 2 O maser emission suggest the presence of a nearby exciting source, that could be also responsible for the excitation of HH 265. Our ammonia map (see Fig. 2.14) shows that both the H 2 O maser and the HH object fall inside the ammonia condensation, but they are displaced by 1. 5( 0.08 pc) to the SE of the position of the ammonia maximum. We suggest that a sensitive

97 2.3. Results 61 Figure 2.13: Same as Fig. 2.7, for the HH 31 region. The NH 3 lowest contour is 0.3 K and the increment is 0.2 K. The positions of the HH 31 knots are from Gómez et al. (1997) search in the submm, mm or cm range in the vicinity of the NH 3 emission peak, could reveal an embedded object, responsible for the excitation of HH 265. The mass derived for this region (see Table 2.7) exceeds the virial mass by a factor of five, a result that may indicate that a significant fraction of the cloud is still undergoing the process of gravitational collpase towards a central, embedded protostar. A 20 cm source, located 2 to the NE of HH 265, was detected by Snell & Bally (1986). However, this source lies outside the ammonia condensation and was not detected at shorter wavelengths (6 cm and 2 mm; Snell & Bally 1986), suggestive of a negative espectral index, characteristic of background extragalactic sources. Unfortunately, sensitive observations reaching the position of the ammonia maximum are not available.

98 62 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.14: Same as Fig. 2.7, for the HH 265 region. The NH 3 lowest contour is 0.3 K and the increment is 0.2 K L1551 NE L1551 NE is a young stellar object in the L1551 molecular cloud. It is located very close ( 2. 5) to the well-studied embedded source L1551 IRS 5. Because L1551 NE is located toward the red lobe of the large IRS 5 outflow, it was difficult to establish whether L1551 NE has its own flow. Moriarty-Schieven, Buttner & Wannier (1995) suggest the presence of a weak molecular outflow from this source and Devine, Reipurth & Bally (1999) concluded that L1551 NE drives a new HH flow (HH 454) and that probably drives the objects HH 28 and HH 29, that were previously atributted to IRS5.

99 2.3. Results 63 Figure 2.15: Same as Fig. 2.7, for the L1634 region. The NH 3 lowest contour is 0.3 K and the increment is 0.15 K. Dashed lines indicate outflow axes discussed in text. IRAS is the proposed exciting source for the HH outflow and the source IRS 7 is the proposed exciting source for the second outflow (knots 4 and 9) We have detected intense ammonia emission towards the position of L1551 NE (see spectrum in Fig. 2.4), but the proximity to IRS 5, that is associated with a strong NH 3 condensation (Torrelles et al. 1983) makes difficult to separate both components. A high angular resolution observations of high density tracers are needed in order to detect the structure of dense gas around L1551NE L1634 L1634 contains two H 2 bipolar jets (Hoddap & Ladd 1995). One of them, HH , is constituted by several H 2 knots symmetrically located from the source IRAS , which has been proposed as the driving source (Hoddap & Ladd 1995;

100 64 Chapter 2. Ammonia towards molecular and optical outflows Davis et al. 1997). The jet extends from east (knots HH 241A-D) to west (knots HH 240A-D). Knots HH 240A and HH 241A were previously known as RNO 40 and RNO 40E (Jones et al. 1984). CO(3 2) observations reveal the presence of a molecular outflow probably associated with IRAS (Davis et al. 1997). The other bipolar jet only has two knotty bow shocks (knots 9 and 4; Hoddap & Ladd 1995; see Fig. 2.15). The near-infrared source, IRS 7, found near the center of the jet, has been proposed as the powering source of this outflow (Hoddap & Ladd 1995; Davis et al. 1997). Both sources are associated with millimeter continuum emission (Chini et al. 1997). Lee et al. (2000) have mapped the CO emission from the molecular outflows, showing a clear correlation in structure and position between the CO and H 2 emission. Beltrán et al. (2001) detect the source IRAS at cm and submm wavelengths and propose it as a Class 0 source, and also concluded that IRS 7 is a very young stellar object. Our map (Fig. 2.15) shows that both sources, IRAS and IRS 7, are associated with dense gas. The NH 3 emission peak is located close ( pc) to the position of the IRAS source. This source has a steeply rising spectral energy distribution through the IRAS bands and it is detected at cm, mm and submm wavelenghts (see references in Table 2.8). These results, together with its association with the ammonia core, suggest that IRAS is a very young object deeply embedded in the high density gas and that it is a very good candidate for exciting the optical jet HH and the molecular outflow. The near-ir source IRS 7 is displaced by 1. 4( 0.19 pc) to the SE of the position of the emission maximum. The association of IRS 7 with high density gas suggest that it is a very young stellar object as suggested by Beltran et al. (2001). We noted that the central velocity of the ammonia lines increases to the west of the peak position. We found a velocity shift of 0.31 km s 1 between the peak position and the position of knot HH 240 A. This knot has a large proper motion away from the IRAS source (Jones et al. 1984). The velocity shift detected could indicate an interaction between the jet and the dense gas RNO 43 RNO 43 (Cohen 1980) is the brightest spot of a chain of Herbig-Haro knots (Jones et al. 1984; Ray 1987; Mundt et al. 1987) extending 5 to the northeast of the

101 2.3. Results 65 source IRAS This chain is designated as HH 243 in the new catalog of Herbig-Haro objects of Reipurth (1994). Another long ( 5 ), well collimated chain of Herbig-Haro knots (HH 245) extends to the north of RNO 43. Reipurth (1991) found a large fragmented counter bow-shock (HH 244) to the southwest of the IRAS source, suggesting that HH 243 and HH 244 constitute a bipolar HH flow. Anglada et al. (1992) found several radio continuum sources that could be related to the HH 243, HH 244 and HH 245 chains. The high-velocity CO emission in the region has been mapped by Edwards & Snell (1984), Cabrit et al. (1988), and Bence et al. (1996). The CO outflow exhibits a complex distribution with several overlapping red and blueshifted lobes, extending on both sides of the IRAS source, and aligned roughly in the north-south direction. The CO lobes located to the north of the IRAS source were initially proposed to constitute two separate outflows (Edwards & Snell 1984). However, no exciting sources have been found for these proposed outflows. Also, no NH 3 emission associated with these northern lobes has been detected (Anglada et al. 1989). On the other hand, Cabrit et al. (1988) proposed that the overall high-velocity structure constitutes a single bipolar CO outflow powered by IRAS A CS clump (Cabrit et al. 1988) is associated with the IRAS source. However, the nominal position of the IRAS source appears to be displaced 1 east from the center of the clump. Anglada et al. (1992) found a 3.6 cm VLA source (also detected at 1.3 mm by Reipurth et al. 1993) which is better centered on the CS cloud. Anglada et al. (1992) suggest that the IRAS catalog position is in error by 30 in right ascension, and that the IRAS and the radio continuum sources are tracing the same embedded object, which is the powering source of both the molecular and the HH outflows. In Fig. 2.16, we show our NH 3 map of this region. We have detected a weak NH 3 condensation centered 1 to the west of the IRAS source, similar to the CS condensation observed by Cabrit et al. (1988). As the exciting sources of outflows are usually deeply embedded objects, the fact that the high-density gas (traced by the CS and NH 3 emission; Cabrit et al. 1988; this chapter) is found associated only with the cm-mm-iras source, and that no NH 3 emission was found associated with the northern CO lobes near RNO 43 (Anglada et al. 1989), further supports that the radio continuum source represents a deeply embedded young stellar object, and is the most plausible powering source for the molecular and HH outflows observed in this region, as suggested by Anglada et al. (1992).

102 66 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.16: Same as Fig. 2.7, for the RNO 43 region. The ammonia lowest contour level is 0.1 K, and the increment is 0.02 K. The central part of the CO bipolar outflow is shown as mapped by Cabrit et al. (1988)

103 2.3. Results 67 Figure 2.17: Same as Fig. 2.7, for the HH 83 region. The ammonia lowest contour level is 0.08 K, and the increment is 0.02 K. The map of the CO bipolar outflow is from Bally et al. (1994). The position of IRAS is indicated HH 83 This HH object lies at the western edge of the L1641 molecular cloud. The optical structure consists of a jet (at least 32 long), apparently emanating from the embedded infrared source HH83 IRS (IRAS ; Reipurth 1989), which is associated with a reflection nebula and ending with a bow-shock. The jet is highly collimated, and presents large variations in velocity and physical conditions along its length (Reipurth 1989). There is a faint nebulosity 44 southeast of the central infrared source that could be part of the counter bow-shock (Reipurth 1989;

104 68 Chapter 2. Ammonia towards molecular and optical outflows Ogura & Walsch 1991). The estimated bolometric luminosity of HH83 IRS is 8 L (Reipurth et al. 1993). This source does not present detectable radio continuum emission at 3.6 and 2 cm (Rodríguez & Reipurth 1994). Bally et al. (1994) have mapped a very low velocity, poorly collimated asymmetric molecular outflow (with the redshifted lobe much larger than the blueshifted one) associated with HH83 IRS. These authors suggest that the outflow from HH83 IRS has blown out of the molecular cloud and that it may be in a late stage of evolution. Interferometric CS observations (angular resolution 7 ) of the cloud core associated with HH83 IRS (Nakano et al. 1994) reveal a high-density structure consisting of a bar ( 15 long, centered on HH83 IRS and nearly perpendicular to the HH jet) and two ridges surrounding the base of the jet. These authors interpret the CS bar as a rotating circumstellar disk and the two ridges as tracing a small elongated hollow that may be playing an important role in focusing the HH jet. We have detected a weak NH 3 clump with the emission peak close to the proposed exciting source of HH 83 (see Fig. 2.17). The NH 3 clump appears unresolved with our beam of 1. 4, and we cannot study the small scale structure observed in CS by Nakano et al. (1994). At a larger scale, the weakest NH 3 emission seems to extend further to the north and to the west, outside our mapped area. The region we mapped in NH 3 corresponds to the core of the molecular clump studied in 13 CO by Bally et al. (1987, 1994), which also shows a clear northern extension HH 84 This HH object was identified and studied by Reipurth (1985, 1989). HH 84 is a long ( 101 ) chain of HH knots outlining a well-collimated optical flow with a position angle of 154. Unlike the large majority of the optical jets, this HH outflow is redshifted with respect to the ambient cloud. Morgan et al. (1991) found evidence for red wing emission in CO profiles, but could not confirm whether this is a molecular outflow. Up to now, no good candidate for the HH flow excitation has been proposed. IRAS (identified with SW Ori, an Hα star and X-ray source; Strom et al. 1989a) lies 2 south along the jet axis (see Fig. 2.18). However, based on the morphology of the knots, Reipurth (1989) argues that the flow exciting source should most probably be an embedded source (still undetected) located to the north of the jet.

105 2.3. Results 69 We found weak ammonia emission associated with the HH knots. Our NH 3 map is presented in Fig The ammonia emission maximum is close to the northern edge of the jet, and may be tracing the location of a possible embedded exciting source, then supporting the suggestion of Reipurth (1989). However, we only mapped a small region and, in particular, our map does not reach the position of the IRAS source. The NH 3 emission appears to extend further to the northeast, roughly following the distribution of the emission of the molecular cloud mapped in 13 CO by Bally et al. (1987; see detail in Reipurth 1989) HH 86/87/88 The Herbig-Haro objects HH 86, HH 87 and HH 88 appear to be closely associated, and probably originate in the same flow (Reipurth 1985, 1989). The three objects are roughly aligned, but they exhibit a rather complex substructure and no local exciting source has been found. The knots in HH 86 appear to cluster around a faint star, but this star is probably not related to the flow, as discussed by Reipurth (1989). The T Tauri star V573 Ori (possibly associated with IRAS ; Weintraub 1990) is also close by, but it does not lie on the line traced by the HH jet. Bally & Devine (1994) suggest that these HH objects are the southern end of a 3 pc long superjet emanating from the exciting source of HH 34. Our NH 3 map is shown in Fig As it can be seen in the figure, the NH 3 emission is faint and displaced to the east of the HH 86/87/88 complex. As the HH 86/87/88 complex lies along a ridge with increasing column density to the east (as mapped in 13 CO by Bally et al. 1987), it is plausible that the NH 3 emission continues further to the east of the region we have mapped. Since no NH 3 emission is seen towards the HH complex, this lack of high-density gas associated with the HH objects seems to exclude that their exciting source could be an undetected deeply embedded object in this region, then favouring a non local origin for the HH excitation, as suggested by Bally & Devine (1994) L1641-N A bipolar CO outflow, L1641-N (Fukui et al. 1986, 1988; Wilking et al. 1990), has been mapped in the northern part of the L1641 cloud. The outflow is centered

106 70 Chapter 2. Ammonia towards molecular and optical outflows on IRAS , which is proposed as the outflow exciting source. Although optically invisible, this source is one of the most luminous (L IR 220 L )IRAS sources in this region. Near-IR images (Strom et al. 1989c, Chen et al. 1993) reveal a dense stellar concentration centered on the IRAS position. The IRAS counterpart has been identified in the near-ir (Chen et al. 1993), millimeter (Wilking et al. 1989, Chen et al. 1995) and centimeter (Mundy et al. 1993, Anglada et al. 1998, Chen et al. 1995) ranges. Recently, H 2 O maser emission has been found in association with IRAS (Xiang & Turner 1995). In addition, several faint red nebulous objects of unknown nature have been found in a CCD image of the region (Reipurth 1985). A centimeter continuum source (Morgan et al. 1990, Anglada et al. 1996), also visible in the CCD image by Reipurth (1985), is found 2 to the NE of the IRAS source, approximately midway between the red nebulous objects Re 35 and Re 43. About 3 to the SW of the center of the L1641-N molecular outflow, lies the source IRAS This source (L bol 86 L )isatypicalclassisource (Strom et al. 1989a). Several near-ir sources (Chen et al. 1993) and a centimeter continuum source (Morgan et al. 1990, Anglada et al. 1998) are found near the IRAS position. Red wing CO emission has been observed towards this position, although it is unclear whether this high-velocity emission originates from IRAS or it is just extended high-velocity emission from the L1641-N outflow (Morgan et al. 1991). We have mapped in NH 3 a region that includes both IRAS sources. The map we have obtained is shown in Fig The NH 3 structure consists of two subcondensations, peaking near the positions of the IRAS sources. This result suggests that both IRAS sources are embedded in dense gas. The condensation around IRAS has been mapped in several molecular species (Fukui et al. 1988; Chen et al. 1992; Harju et al. 1991; McMullin et al. 1994) with the emission peaking close to the IRAS position as in our NH 3 map. In particular, the NH 3 map obtained by Harju et al. (1991) with higher angular resolution (40 ), is in good agreement with our results. The whole region encompassing both IRAS sources was mapped previously only in HCN (Takaba et al. 1986) and with lower ( 3 ) angular resolution. CS emission was detected but not mapped, towards the two IRAS sources (Morgan & Bally 1991).

107 2.3. Results 71 Figure 2.18: Same as Fig. 2.7, for the HH 84 region. The ammonia lowest contour level is 0.08 K, and the increment is 0.02 K. The position of IRAS (identified as SW Ori) is indicated.

108 72 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.19: Same as Fig. 2.7, for HH 86/87/88 region. The ammonia lowest contour level is 0.12 K, and the increment is 0.04 K. The position of IRAS (possibly associated with V573 Ori) is indicated.

109 2.3. Results 73 Figure 2.20: Same as Fig. 2.7, for L1641-N region. The ammonia lowest contour level is 0.15 K, and the increment is 0.15 K. The IRAS source associated with the northern ammonia peak is IRAS and the one associated with the southern ammonia peak is IRAS The map of the CO outflow is from Fukui et al. (1986) IRAS IRAS was proposed as the exciting source of a bipolar molecular outflow (Snell et al. 1990). Tofani et al. (1995) detected four H 2 O maser spots close to the IRAS position. We found a condensation elongated in the north-south direction (Fig. 2.21). The NH 3 emission peaks at the position of the IRAS source. This positional coincidence,

110 74 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.21: Same as Fig. 2.7, for the region around IRAS The NH 3 lowest contour is 0.3 K and the increment is 0.2 K. The CO bipolar outflow is from Snell et al. (1990) its relation with H 2 O maser emission, along with the fact that its infrared emission increases steeply towards longer wavelenghts, suggests that IRAS is a very young stellar object, deeply embedded in the high density gas, favoring this object as driving source of the molecular outflow L1641-S3 L1641-S3 is a bipolar CO outflow located in the southern part of the L1641 cloud (Fukui et al. 1989, Wilking et al. 1990, Morgan et al. 1991). The outflow is centered on the source IRAS (= FIRSSE-101), which has been proposed as the outflow exciting source. The IRAS source is associated with H 2 O maser emission

111 2.3. Results 75 (Wouterloot & Walmsley 1986) and with an H II region (Hughes & MacLeod 1994). The IRAS counterpart has been identified in the near-infrared, centimeter and millimeter ranges and strong submillimeter emission has been detected towards the IRAS position (see Table 2.8). The NH 3 spectra show two components in all the hyperfine lines, in all the positions where emission is detected. There are clearly two velocity components, one at 3.8 km s 1 and the other at 4.9 km s 1. Each velocity component peaks at a different position. In Fig we show the observed espectra at the position of the emission peak for each velocity component. The observed velocities appears to be the result of two distinct clumps of emission with a velocity separation of 1 km s 1 along the line of sight. Figure 2.22: Spectra of the NH 3 (1,1) emission at (0, 0) and ( 2.8, 0), thepositions of the emission maximum for each velocity component of L1641-S3. Offsets are with respect the position given in Table 2.3. We have separated the maps in two velocities. The map of the component at 4.9 km s 1 (Fig. 2.23) reveals an NH 3 condensation with the emission maximum located at the position of IRAS The main axis of this condensation is elongated roughly in the NW-SE direction, perpendicular to the outflow axis. We have detected emission towards the NE, close to the position of IRAS and IRAS Both sources are not detected at submillimeter wavelenghts

112 76 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.23: Same as Fig.2.7, but for the emission associated with the component at 4.9 km s 1 for the L1641-S3 region. The NH 3 lowest contour is 0.3 K and the increment is 0.2 K. The map of the CO bipolar outflow is from Morgan et al. (1991) (Dent et al. 1998) and only IRAS has a near-ir counterpart (Strom et al. 1989). Our observations do not reach the position of these two sources, but as the NH 3 emission seems to extend to the NE, these IRAS sources may be associated with high density gas. The map of the component at 3.8 km s 1 is shown in Fig No emission is detected towards the NE, thus it seems that this cloud is not associated with any of the IRAS sources located in the region. Only IRAS is associated with this component of dense gas, but we cannot establish it this is a real association or a projection effect. The positional coincidence between IRAS and the emission maximum

113 2.3. Results 77 Figure 2.24: Same as Fig.2.7, but for the emission associated with component at 3.8 km s 1 for the L1641-S3 region. The NH 3 lowest contour is 0.4 K and the increment is 0.2 K. The map of the CO bipolar outflow is from Morgan et al. (1991) of high velocity gas, along with the fact that the IRAS fluxes increase to longer wavelengths and that it is detected at cm, mm and sub-mm ranges, suggest that IRAS is a very young object deeply embedded in the high density gas and associated only with the high velocity clump. The NH 3 map obtained by Harju et al. (1993) with higher angular resolution (40 ) is in good agreement with our results for the component at 4.9 km s 1.

114 78 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.25: Same as Fig.2.7, but for the CB 34 region. The NH 3 lowest contour is 0.15 K and the increment is 0.1 K. The three optical jets discussed in text are indicated by dotted lines. The map of the CO bipolar outflow is from Yun & Clemens (1994a) CB 34 The small Bok globule CB 34 (Clemens & Barvainis 1988) contains a single IRAS source, IRAS , which is the proposed driving source of a bipolar molecular outflow (Yun & Clemens 1994a). IRAS has a near-infrared counterpart and it has been detected also at submillimeter, millimeter and centimeter wavelenghts (see references in Table 2.8). Alves & Yun (1995) found in near-ir images a small aggregate of YSOs embedded in the globule. Alves (1995) discovered, from optical and n-ir images, a variable object, CB34V, which has been identified as an embedded PMS object (Alves et al. 1997). Moreira & Yun (1995) discovered four Herbig-Haro objects (HH 290S, HH 290 N1, HH 290 N2 and HH 291) and several H 2

115 2.3. Results 79 structures (labeled Q1, Q2, Q3, Q4, hh291x and hh291y) in this region. Moreira & Yun (1995) suggested that the objects HH 290S/N1/N2 constitute a jet driven by an embedded near-ir source (HH 290 IRS, a member of the near-ir aggregate of YSOs), that the structure Q1-Q4 is a well collimated jet driven by an embedded object (labeled Q, a member of the near-ir agreggate of YSOs) and that hh291x, hh291y and HH 291 could be bright knots of an embedded jet, whose driving source remains undetected. The ammonia structure, unresolved with our beam, peaks close to the position of IRAS (see Fig. 2.25), in good agreement with the results of others highdensity tracers (CS, Launhardt et al. 1998; HCN, Afonso et al. 1998; NH 3, Codella & Scappini 1998). The sources HH 290 IRS and CB34V appear in projection toward the ammonia core, suggesting that they are young stellar objects embedded in the dense molecular gas and, thus, good candidates for the excitation of the outflows. The HH 291 jet, two of whose knots are only detected in the near-ir, also appears projected toward the high density gas, in agreement with the suggestion of Moreira & Yun (1995) that they may be tracing an embedded jet. We suggest that the exciting source of this jet could be located in the line connecting the knots and close to the position of the emission maximum. High resolution observations could reveal the position of this embedded object. The source Q lies at the edge of the condensation L1617 A map of the overall L1617 region where NH 3 emission is detected is shown in Fig The map encloses the ammonia condensations associated with HH 270/110 and HH 111 and their molecular outflows. HH 270/110 HH 110 is a well collimated jet located in the L1617 molecular cloud (Reipurth & Olberg 1991). Reipurth, Raga & Heathcote (1996) discovered a second jet, HH 270, 3 NE of HH 110 and proposed HH 270 IRS, a difusse near-ir source, as the exciting source. HH 270 IRS lies close to IRAS , whose properties are consistent with those of typical HH driving sources; however the association

116 80 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.26: Ammonia cores in L1617 (thick contours) overlapped on the CO outflow maps of Reipurth & Olberg (1991) (thin contours; solid contours indicate blushifted gas and dashed contours indicate redshifted gas). Close-ups of the clumps of the N-W region (associated with HH 270/110 and SE region (associated with HH 111) are shown in Figs and Ammonia contour levels are the same as in these figures. Small crosses indicate observed positions, big crosses indicate infrared sources, filled triangles indicate Herbig-Haro objects and dots indicate radio continuum sources. Additional points were observed near HH 113 ( 12 east). The half power beam of the telescope is shown as a circle.

117 2.3. Results 81 Figure 2.27: Same as Fig. 2.7, for the HH 270/110 region. The NH 3 lowest contour level is 0.2 K and the increment is 0.15 K. The sources discussed in text are indicated. between the IRAS source and HH 270 IRS has not been confirmed (Reipurth, Raga & Heathcote, 1996). These authors suggest that the HH 270 jet suffers a grazing collision with a nearby molecular cloud core, thus producing a deflected flow, which is manifested as the HH 110 jet. This scenario was supported by the VLA detection of HH 270 IRS at cm wavelenghts (Rodríguez et al. 1998). These observations revealed that this source (VLA 1) is elongated along the axis of the HH 270 jet, suggesting that VLA 1 traces the base of the jet that excites the HH 270/110 system. This scenario is in full agreement with our NH 3 results. About 3 to the SW of HH 270 IRS, lies the source IRAS Reipurth & Olberg (1991) discovered a bipolar molecular outflow (see Fig. 2.26) centered on this IRAS source. Davis et al. (1994) detected two near-infrared objects (IRS 1 and

118 82 Chapter 2. Ammonia towards molecular and optical outflows IRS 2) within a few arsec from the nominal IRAS position. Davis et al. (1994) and Garnavich et al. (1997) showed that IRS 1 is a bright stellar object, while IRS 2 appears as a diffuse nebula, and reported the discovery of two highly collimated H 2 jets, aligned in the north-south direction, apparently emanating from these near-ir objects (see Fig. 2.26). Reipurth & Olberg (1991) and Davis et al. (1994) associated IRS 1 with the IRAS source, while Garnavich et al. (1997) identified a faint near-ir object (labeled GNRB 7) as the IRAS counterpart. Rodríguez et al. (1998) detected a cm VLA source (VLA 2) located 4 north of IRS 2 and between the two H 2 jets lobes. These authors identified VLA 2 as the IRAS counterpart and with the driving source of the IRS 2 H 2 bipolar jet. Our ammonia map (Fig. 2.27) shows two high density clumps separated by 0.4 pc. These two NH 3 clumps peak close to the positions of two local maxima in the 13 CO extended structure mapped by Reipurth, Raga & Heathcote (1996). The emission of the eastern NH 3 clump peaks at the position of HH 270 IRS/VLA 1, suggesting that it is embedded in the high density gas, giving support to its identification as the powering source of the HH 270 jet. The source IRAS lies 1 west from the NH 3 peak and is probably associated with high density gas. The HH 110 flow appears associated with the western core, which is located at the point where the HH 270/110 flow changes abruptly its direction, suggesting that this western core is responsible of the collision and deflection of the HH 270 flow, giving support to the scenario proposed by Reipurth, Raga & Heathcote (1996). The NH 3 western clump peaks near the positions of IRAS , IRS 2/VLA 2 and IRS 1 (see Fig. 2.27). This result, together with the fact that the energy distribution of the IRAS source is strongly rising towards longer wavelengths, suggest that all these sources maybe embedded objects, giving support to their identification as the driving sources of either the molecular outflow and the H 2 jets. The remaining five cm continuum sources detected in the region by Rodríguez et al. (1998) (see Fig. 2.27) have a negative spectral index, characteristic of nonthermal emission. One of them (VLA 4) could be associated with the knot HH 110 H and the others are probably background objects unrelated with the star-forming region.

119 2.3. Results 83 Figure 2.28: Same as Fig. 2.7, for the HH 111 region. The NH 3 lowest contour level is 0.15 K and the increment is 0.07 K. HH 111 HH 111 is a well collimated jet located in the L1617 cloud. Reipurth & Oldberg (1991) discovered a highly collimated molecular outflow associated with HH 111 and proposed IRAS as the driving source of the molecular and optical outflows. The IRAS source is associated with a cm radio continuum source, VLA 1, (Rodríguez & Reipurth 1994, Anglada et al. 1998b). Reipurth, Bally & Devine (1997) proposed that HH 113 and HH 311, belong to the HH 111 outflow, constituting a giant outflow with a total extent of 7.7 pc( 1 ). Gredel & Reipurth (1993) detected a H 2 bipolar jet almost perpendicular to HH 111, called HH 121, which appears to emanate from the IRAS/VLA 1 source. The VLA 1 source, detected also

120 84 Chapter 2. Ammonia towards molecular and optical outflows in near-ir, has recently been resolved as a quadrupolar radio jet, whose axes are nearly parallel to those of the HH 111 and HH 121 outflows (Reipurth et al. 1999). These authors detect an additional cm source, VLA 2, 3 NW of VLA 1, associated with a new near-ir source (star B), which exhibits some evidence of driving its own outflow. Reipurth et al. (1999) proposed that VLA 1 is a close binary with a projected separation of less than 0. 1 (50 AU) and speculated that the VLA 1 binary and the VLA 2 source originally formed an unstable non-hierarchical triple system from which VLA 2 was ejected. The NH 3 map (Fig. 2.28) shows a condensation with the emission peaking near the positions of the proposed triple system. The energy distribution of the IRAS source is steeply rising towards longer wavelenghts. Altogether suggests that the sources are deeply embedded in the high density gas. The remaining radio continuum sources detected in the region (Anglada et al. 1998b) are not associated with dense gas and have negative spectral indexes, indicating that probably almost all are non-thermal background sources unrelated with the region. HH 113 We observed a five-point map around HH 113 (not shown in the figure), which is located about 12 arcmin to the east of the HH 111 complex. We did not detect significant emission in any of these positions. Reipurth, Bally and Devine (1997) suggest that HH 113 is the eastern boundary of the HH 111 complex. The lack of dense gas around this object, together with the fact that there are no sources at its vicinity, suggest a non local origin for this object, giving support to its identification as part of the HH 111 complex IRAS IRAS lies 5 east of the H II region S242. This IRAS source has been proposed as the exciting source of a poorly collimated molecular outflow (Snell et al. 1990), althought this source is displaced by 1 SE from the geometrical center of the outflow. A 6 cm radio continuum source has been detected close to the position

121 2.3. Results 85 Figure 2.29: Same as Fig. 2.7, for the region around IRAS The NH 3 lowest contour is 0.2 K and the increment is 0.1 K. The center of the near-ir cluster (Carpenter et al. 1993) is indicate, that extends over a region of 1 pc in size. The CO bipolar outflow is from Snell et al. (1990) of the IRAS source (Carpenter et al. 1990). A near-ir cluster, extending over a region of 1 pc in size, was detected in the region (Carpenter et al. 1993). These authors concluded that many of the cluster members have colours similar to those of protostars, suggesting star-formation activity close the center of the region. ThecondensationwehavemappedinNH 3 (Fig. 2.29) has the emission peak displaced 1 ( 0.7 pc) to the north of the IRAS source position. However, the position of the NH 3 emission maximum is close to the the center of the outflow and to the near-ir cluster center, suggesting that some cluster members could be embedded stellar objects, in agreement with Carpenter et al. (1993). The position of the NH 3 maximum roughly coincides with a CS emission peak (Carpenter et al.

122 86 Chapter 2. Ammonia towards molecular and optical outflows 1993). Our observations will favor a source located northern to the IRAS position as a plausible exciting source. Sensitive cm continuum observations towards this position could reveal this object CB 54 CB 54 is a Bok globule associated with the source IRAS , which has been proposed as the exciting source of a highly collimated bipolar molecular outflow (Yun & Clemens 1994a). The IRAS source is double in the near-ir (two components separated 12 ), (Yun & Clemens 1994b) and is detected also in cm (Yun et al. 1996; Moreira et al. 1997) and mm wavelenghts (Launhardt & Henning 1997). We found a compact NH 3 condensation (Fig. 2.30) with the emission peaking at the position of the IRAS source. This result, together with the fact that the IRAS source has a cm radio continuum counterpart and that its spectral energy distribution is steadily rising to longer wavelenghts, suggest that the IRAS source is a very young object deeply embedded in the high density gas favors it as the exciting source L100 L100 (Barnard 62) is a large, very opaque Bok globule in Ophiuchus, surrounded by bright rims. Reipurth & Gee (1986), based on a photometric study, estimate a distance of 225 ± 25 pc. These authors found several Hα emission stars associated with L100 and conclude that IRAS (0.25 L L L ), an IRAS source with no optical counterpart, represents the envelope of an embedded PMS object, more evolved than a protostar. Parker et al. (1988) detected a bipolar molecular outflow elongated in the NE-SW direction and centered at the position of IRAS , which was proposed as the outflow exciting source. We have mapped in NH 3 the region around IRAS We have detected faint and unresolved NH 3 (1,1) emission peaking near the position of the IRAS source. Our map is shown in Fig The IRAS position is near the maximum of the ammonia map, in agreement with the idea that it is an object embedded in highdensity gas. However, the weakness of the ammonia emission suggests that it is

123 2.3. Results 87 Figure 2.30: Same as Fig. 2.7, for the CB 54 region. The NH 3 lowest contour is 0.25 K and the increment is 0.1 K. The CO bipolar outflow is from Yun & Clemens (1994a) associated with only a small amount of high-density gas and that the size of the ammonia clump could be much smaller than our beam L483 Parker et al. (1988, 1991) and Fuller et al. (1995) have mapped in CO a compact bipolar molecular outflow in the L483 dark cloud. The outflow is clearly elongated along the E-W direction and it is centered on the low-luminosity infrared source IRAS (L =14L, assuming a distance of 200 pc; Ladd et al. 1991a), which is proposed as the outflow exciting source. This source has neither optical nor near-infrared counterpart (Parker 1991). The source has been detected with the VLA at 3.6 cm ( Anglada et al. 1996). From the far-ir data and from submillimeter observations (Ladd et al. 1991b; Fuller et al. 1995), Fuller et al. (1995) conclude

124 88 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.31: Same as Fig. 2.7, for the L100 region. The ammonia lowest contour level is 0.08 K, and the increment is 0.02 K. The map of the CO outflow is from Parker et al. (1988). that the IRAS source is a very young object similar to the so-called Class 0 sources. The source is surrounded by a bipolar near-ir nebula, and a jet-like region of H 2 emission, ending in a bright knot, extends along the blue lobe of the CO outflow (Fuller et al. 1995). An H 2 O maser near the IRAS position has been detected by Xiang & Turner (1995) through single-dish observations. In Fig we show the ammonia map obtained from our observations. The NH 3 emission peaks very close to the IRAS source position. This fact, together with the infrared results (Fuller et al. 1995), suggest that the IRAS source is deeply embedded in the dense core, giving support to its identification as the powering source of the molecular outflow. Our ammonia map is in good agreement with the ammonia map shown by Fuller & Myers (1993). Fuller & Myers (1993) found two

125 2.3. Results 89 Figure 2.32: Same as Fig. 2.7, for the L483 region. The ammonia lowest contour level is 0.20 K, and the increment is 0.15 K. The map of the CO outflow is from Parker et al. (1988). velocity components separated by 0.28 km s 1 in an NH 3 spectrum obtained towards the peak of the core, and discuss on their relationship with the overall distribution of dense gas. The velocity resolution of our observations ( 0.2 kms 1 )doesnot allow us to separate these components in the spectra. Goodman et al. (1993) report a velocity gradient ( 1.9 ± 0.2 kms 1 pc 1,P.A.=52 ) in the region. From our data, we estimate a velocity gradient of 2 3 km s 1 pc 1 approximately in the SW-NE direction, which is consistent with the result of Goodman et al. (1993).

126 90 Chapter 2. Ammonia towards molecular and optical outflows L379 The dark cloud L379 contains the bright source IRAS , which was proposed as the exciting source of a bipolar molecular outflow (Hilton et al. 1986; Wilking et al. 1990). The red- and blue-wing emission overlap for most the extension of the outflow, but the emission maxima are not coincident. This structure has been interpreted as two outflows centered north and south of the IRAS source (Kelly & McDonald 1996). Observations at millimeter and submillimeter wavelenghts have revealed two distinct clumps of dust continuum emission positioned several arcsec northwest and southwest, respectively from the IRAS nominal position (McCutcheon et al. 1995; Kelly & Mcdonald 1996). Kelly & McDonald (1996) suggest that the dust clumps probably contains the driving sources of the molecular outflows. We found an NH 3 condensation (Fig. 2.33) with the emission peaking at the position of IRAS The spectral energy distribution of this IRAS source rise steeply at longer wavelenghts. Altogether suggest that the IRAS source is a deeply embedded object. Both smm sources appear to be associated with NH 3 emission, but our angular resolution does not allow us to favor one of them in terms of the proximity to the NH 3 maximum. The physical parameters we have obtained for this condensation (Table 2.7) indicate that L379 is a massive region (M M ). The estimated luminosity of the IRAS source is L bol L (Kelly & McDonald 1996). The high NH 3 mass obtained, together with the high luminosity of the source, could indicate that this source is a massive protostellar object, and thus that L379 is a high-mass star forming region. Our results are in agreement with the C 18 O results obtained by Kelly & McDonald (1996) with an angular resolution of 20.OurNH 3 map, as well as the C 18 O map, shows a single emission maximum. Kelly & MacDonald (1996) found two velocity components in the C 18 O spectra, separated by 2kms 1,that they interpreted as the result of two distinct clumps of emission. Although our ammonia line are broad, a hint of the 2 components can be appreciated in the satellite lines (see Fig. 2.4).

127 2.3. Results 91 Figure 2.33: Same as Fig. 2.7, for the L379 region. The NH 3 lowest contour level is 0.3 K and the increment is 0.2 K. The position of the two dust clumps is indicated by asteriscs. The map of the CO bipolar outflow is from Kelly & Macdonald (1996) L588 Reipurth & Eiroa (1992) discovered two isolated Herbig-Haro objects, HH 108 and HH 109, in this region and proposed IRAS as the driving source of the objects. Ziener & Eislöffel (1999) found that both HH objects consists of several bright knots, some of them with H 2 counterpart. Chini et al. (1997) found two 1.3 mm sources, the stronger is coincident with the IRAS source and the fainter, HH 108 MMS, has no counterpart. At present, it is unclear which one of these two sources is the driving source of the HH objects. Parker et al. (1991) detected broad line wings in CO spectra taken towards the IRAS position. The NH 3 map (Fig. 2.34) shows a condensation elongated in the NE-SW direc-

128 92 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.34: Same as Fig. 2.7, for the L588 region. The NH 3 lowest contour is 0.3 K and the increment is 0.15 K. The positions of the HH 108 and HH 109 knots are from Ziener & Eislöffel (1999). tion, similarly to the molecular cloud mapped in CO by Parker et al. (1991). The ammonia emission maximum is located at the position of IRAS This result, along with the fact that this source has a rising energy distribution towards longer wavelenghts and presents strong millimeter emission, suggest that the IRAS source is a very young object deeply embedded in the high-density gas. Although the source HH 108 MMS is located inside the NH 3 condensation, it is displaced 1. 2( 0.1pc) to the NE of the emission peak. Due to its association with the NH 3 emission peak, it appears that the source IRAS is the deepliest embedded object and constitutes a very good candidate for the energy source of the

129 2.3. Results 93 HH complex. From our data, we found that the mass of this region exceeds the virial mass by more than a factor of five (see Table 2.7). This result could indicate that the cloud is in process of gravitational collapse L673 The distance to the L673 dark cloud is not well established. Estimates by different authors range between 150 pc and 400 pc. We will adopt a distance of 300 pc, based on proper motions studies (Herbig & Jones 1983). Armstrong & Winnewisser (1989) discovered a very extended (10 15 ) bipolar molecular outflow in the northern part of L673. There are four IRAS point sources within five arcmin of the center of the outflow. From an analysis of the IRAS colours, Armstrong & Winnewisser conclude that IRAS is probably a visible main-sequence star, while the IRAS colours of the other three sources (IRAS , , ) are consistent with those of embedded stars. In particular, the source IRAS , which coincides with RNO 109 (Cohen 1980), is proposed by Armstrong & Winnewisser (1989) as the most likely candidate to be the outflow exciting source. Ladd et al. (1991a, b) obtained far-infrared photometry and images of IRAS and IRAS , showing that a large fraction of the luminosity of these objects is radiated at long wavelengths (λ >60 μm), indicating that they are very young. This region was mapped in CS by Morata et al. (1997). The CS main emission peak is located 8 to the south-east of IRAS Morata et al. (1997) also found a faint, extended CS emission with two local maxima, coinciding with IRAS and with IRAS Our ammonia map is shown in Fig The ammonia structure consists of four subcondensations, three of them peaking near the positions of the sources IRAS (RNO 109), IRAS and IRAS This result suggests that the three sources are embedded in dense gas. Of the three sources IRAS is the one close that is assocaited with strong emission maximum, suggesting that this source is associated with a large amount of high-density gas, being probably the most deeply embedded of these three objects. The spectral energy distribution of this source (Armstrong & Winnewisser 1989; Ladd et al. 1991a) is also consistent with this suggestion. The source IRAS is also

130 94 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.35: Same as Fig. 2.7, for the L673 region. The ammonia lowest contour level is 0.45K, and the increment is 0.3 K. The IRAS sources associated with the ammonia structure are (from north to south) IRAS (RNO 109), IRAS and IRAS The IRAS source outside the ammonia structure is IRAS The map of the CO outflow is from Armstrong & Winnewisser (1989)(solid contours indicate redshifted gas and dashed contours indicate blueshifted gas). well centered in between the two outflow lobes, despite of the irregular geometry of the molecular outflow (see Fig. 2.35). Taking into account the ammonia results, the spectral energy distribution, and the location with respect to the CO outflow, we favour IRAS (rather than IRAS = RNO 109) as the best candidate for the excitation of the molecular outflow in the region. The strongest NH 3 emission maximum is located at the southest edge of the structure, displaced 1. 4 to the south of the CS emission peak. Up to now, no

131 2.3. Results 95 source has been found in association with this clump. Given the large density of YSOs that appears to be present in this region, it is likely that the southeastern clump could harbor a very deeply embedded object. A sensitive search in the submm, mm or cm range could reveal this embedded object. Although our observations do not reach the position of IRAS , from the region we have mapped it seems clear that the NH 3 emission decreases as one moves to the northeast, towards the position of this IRAS source. Thus, this source does not appear to be associated with a significant amount of dense molecular gas. This result is confirmed by the CS (J=1 0) observations of Morata et al. (1997). Even though the CS emission appears to be more extended than the NH 3 emission, the CS map shows that IRAS lies at the outer edge of the CS distribution, suggesting that this source is not embedded in high density gas. These results are in agreement with those of Armstrong & Winnewisser (1989), which concluded that the IRAS colours of this source are typical of a visible main-sequence star IRAS Bachiller et al. (1995) mapped a molecular outflow consisting of three pairs of lobes emanating from the vicinity of IRAS , suggesting two or three independent outflows driven by different young sources embedded in the core. Chen et al. (1997) found a cluster of near-ir sources around IRAS , which extends to the northwest in the direction of another IRAS source, IRAS Within the cluster, Chen et al. identified three subclusters: subcluster A, which coincides with IRAS and is associated with strong near-ir nebulosity; subcluster B, which shows low extinction; and subcluster C, which is close to the source IRAS and shows moderate extinction. The NH 3 condensation (Fig. 2.36) shows two strong emission peaks, very close to the positions of the IRAS sources of the region, suggesting that both sources are associated with high density gas. This structure is consistent with two clumps. The velocity of the two maxima differs by 2kms 1 (see Table 2.4). In Fig we show a position-velocity diagram along the northwest-southeast direction. The observed difference in velocity is consistent with a gravitationally bound rotational motion of the two clumps.

132 96 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.36: Same as Fig.2.7, but for the region around IRAS The NH 3 lowest contour level is 0.4 K and the increment is 0.15 K. The centers of the three near- IR subclusters found by Chen et al. (1997) are indicated. The map of the CO multipolar outflow is from Bachiller et al. (1995). The source IRAS , which is associated with the densest NH 3 clump (see Table 2.7) and with a CS emission peak (Bachiller et al. 1995), has a steeply rising spectral energy distribution. At cm wavelengths it was resolved into two components at subarsec scale (Anglada et al. 1998a). Millimeter observations around this source (Choi et al. 1999) reveal four mm sources within an area of radius 25, two of them, which are separated 20, are suggested to be protostellar collapse candidates. The second NH 3 clump is associated with IRAS This source was barely detected in the IRAS 12 and 25 μm bands (2.3 Jy in both bands), but is very

133 2.3. Results 97 Figure 2.37: Position-velocity diagram of the NH 3 (1,1) main line along the NW-SE direction (p.a.= 45 ), centered on IRAS The 1. 4 offset corresponds to the position of IRAS The lowest countour level is 0.4 K and the increment is 0.15 K bright at longer wavelenghts (flux densities are and Jy in the 60 and 100 μm IRAS bands, respectively). A cm continuum source (Anglada et al. 1998a) and a near-ir subcluster (Chini et al. 1997) are detected in association with this source. All these results suggest that IRAS is a young stellar object deeply embedded in the high density gas. Bachiller et al. (1995) detected weak extended CS emission towards this source, and thus they cannot confirm the association of this source with the cloud. From our results, we suggest that IRAS is related with the core IRAS IRAS (L = (D/4 kpc) 2 L ; Odenwald & Schwartz 1993) is associated with a compact molecular cloud located in the Cygnus region. The dis-

134 98 Chapter 2. Ammonia towards molecular and optical outflows tance to this source is very uncertain (0.4 kpc D 4 kpc; Little et al. 1988). We adopt its largest value (4 kpc); thus, most of the physical parameters obtained for this region will be upper limits. Little et al. (1988) mapped in 12 CO and HCO + a bipolar molecular outflow associated with this IRAS source, concluding that the outflowing gas has a dense and clumpy nature. We have detected a compact ammonia condensation (Fig. 2.38), with the emission peaking very close to the IRAS position. This result suggests that the IRAS source is deeply embedded in the high density gas, as usually are the exciting sources of molecular outflows. The ammonia lines in this condensation are significantly wider (ΔV km s 1 ) than in the other regions of our sample (see Table 2.2). Moreover, there is a north-south velocity gradient in the NH 3 condensation, with the line velocity in the northern part being redshifted (by 0.5 km s 1 ) with respect to the southern part, i.e., roughly in the same direction as the outflow. These results suggest that the dense gas around IRAS is perturbed by the outflow from this star and is entrained into the high velocity gas, in agreement with the HCO + results obtained by Little et al. (1988). Palla et al. (1991) detected H 2 O maser emission on January 30, 1989 in a single observation towards the position of the IRAS source, obtaining a peak line flux S ν 45 Jy and a radial velocity V LSR = 1.1 kms 1. We detected this H 2 Omaser on February 10, From a seven-point map centered on the IRAS position, we found that the maximum of emission was displaced 1 to the NW of the IRAS source. In Fig. 2.3, we show the spectrum of the H 2 O maser towards this position. The single feature we observed can be fitted with a Gaussian profile having peak line flux S ν =4.4 ± 0.9 Jy, half-power full width ΔV =1.0 ± 0.1 kms 1,and radial velocity with respect to the local standard of rest, V LSR = 1.09 ± 0.07 km s 1.Thus,thisH 2 O maser feature shows high variability on a time scale of one year. Several new maser features, at different velocities appeared also in observations carried out in 1990 and 1991 (Xiang & Turner 1995). One of these features coincides within 4 with the position of the IRAS source V1057 Cyg V1057 Cyg belongs to the small group of the FU Orionis type stars. Before its flare-up in 1970, it was a T Tauri star. A marginally resolved outflow was reported

135 2.3. Results 99 Figure 2.38: Same as Fig. 2.7, for the IRAS region. The ammonia lowest contour level is 0.20 K, and the increment is 0.1 K. The map of the CO outflow is from Little et al. (1988). by Levreault (1989). They detect only a blue wing extending to the north, although no contour map is shown. We have detected very weak ammonia emission towards this source and the line analysis was carried out by averaging several positions, so no contour map could be made. This weak emission indicates that the source is not associated with large amount of high density gas, unless the emission was very compact and heavily diluted in our beam. The lack of high-density gas is in agreement with th fact that the source is optically visible.

136 100 Chapter 2. Ammonia towards molecular and optical outflows L1228 L1228 is a high galactic latitude dark cloud, whose distance is poorly known. Haikala et al. (1991) estimate a distance between 100 and 200 pc, while Bally et al. (1995) argue that a better value is 300 pc. In this work we have adopted this last value. Haikala & Laureijs (1989) discovered a large ( pc 0.8 pc, for the assumed distance of 300 pc) and well-collimated bipolar CO outflow, with its axis in the NE-SW direction. The outflow is centered on the low luminosity object IRAS (L 4 L ), which was proposed as the outflow exciting source. Anglada et al. (1996) have detected this source in the radio continuum at 3.6 cm with the VLA. Very recently, Bally et al. (1995) have obtained a new CO map of the outflow and detected several HH objects along the axis of the molecular outflow. Moreover, these authors detected an H 2 jet emerging from IRAS , but the jet axis differs from that of the molecular outflow by 40, suggesting that the jet ejection direction varies over time. Bally et al. (1995) also detected a long highly collimated HH jet (HH 200), which may be associated with a very low velocity and faint blueshifted CO lobe, and whose exciting source appears to be an embedded T Tauri star located 1. 5 NW of the IRAS source. Tafalla et al. (1994) have observed the dense gas around the IRAS source as traced by C 3 H 2 and HCN. These authors found sudden shifts in the line velocity of these molecules, with a systematic velocity pattern that agrees in direction and velocity sense with the CO outflow. Tafalla et al. (1994) identified three distinct velocity components in the core, and interpreted these results as evidence for the disruption of the dense core by the bipolar outflow from the IRAS source. Our ammonia map of this region (Fig. 2.39) shows a condensation of 3 2 in size, elongated in the N-S direction. The ammonia emission peaks very close to the position of the IRAS and radio continuum source, suggesting that this source is deeply embedded in the high density gas, as it is expected for the exciting source of the outflow. For positions with good signal-to-noise ratio, our data show a velocity shift in the ammonia line velocity, consistent with the direction and sense of the bipolar molecular outflow. In Fig we show the spectra of the NH 3 (1,1) main line observed towards the position of the IRAS source, as well as towards two additional positions displaced 1. 4totheeastand1. 4 to the west, respectively. As it can be seen in the figure, the central velocity of the lines are clearly displaced, with a velocity shift between the extreme positions of 0.54 km s 1, corresponding to a velocity

137 2.3. Results 101 Figure 2.39: Same as Fig. 2.7, for the L1228 region. The ammonia lowest contour level is 0.20 K, and the increment is 0.15 K. The map of the CO bipolar outflow is from Haikala & Laureijs (1989). gradient of 2.2 kms 1 pc 1. Tafalla et al. (1994), from their higher angular resolution data, obtained velocity gradients of up to 10 km s 1 pc 1 on a scale of 20. Our lower angular resolution data do not allow us to detect these sudden shifts in velocity but, in any case, they provide evidence that the dense gas is perturbed and accelerated by the molecular outflow CB 232 This Bok globule is associated with IRAS , which is proposed to be the exciting source of a poorly collimated bipolar molecular outflow (Yun & Clemens 1994a). Yun & Clemens (1995) reported a near-ir counterpart (CB 232YC-I) to the IRAS source. Huard et al. (1999) detected two compact submillimeter sources (SMM1 and SMM2). The submillimeter source SMM1, the brighter of the two, lies 10 distant from the near-ir source and is proposed as Class 0 canditate. The

138 102 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.40: Spectra of the NH 3 (1,1) main line towards three selected positions in L1228. The offsets are in arc minutes with respect to the IRAS position. To make easiest the comparison, the main brightness temperature of the (0,0) spectrum has been divided by 3. position of SMM2 is 5 from the near-ir source, but Huard et al. (1999) cannot determinate if it is a smm counterpart of the near-ir source or a different source that also would be a class 0 candidate. Millimeter continuum emission towards the IRAS position was reported by Launhardt & Henning (1997). We have detected an ammonia condensation (see Fig. 2.41) unresolved by our beam, whose emission peak lies coincides with the position of the IRAS source. The spectral energy distribution of the IRAS source is rising towards longer wavelenghts. Taking into account all results, we suggest that the IRAS source and the smm sources are very young objects deeply embedded in the high density gas and that the globule is a site of very recent star formation IC 1396E IC 1396E is a partially ionized globule (PIG) located at the edge of the H II region IC Wilking et al. (1990) mapped a bipolar molecular outflow and proposed IRAS as the exciting source. Wilking et al. (1993) detected six near-ir sources, one of which, IRS 2, was identified as the IRAS couterpart and coincides

139 2.3. Results 103 Figure 2.41: Same as Fig. 2.7, for the CB 232 region. The NH 3 lowest contour is 0.2 K and the increment is 0.1 K. The CO bipolar outflow is from Yun & Clemens (1994a) with a 2.7 mm continuum source (Wilking et al. 1993). The NH 3 condensation (Fig. 2.42) is somewhat elongated in the north-south direction. The ammonia emission peak is located very close to the position of IRAS , in agreement with the CS and NH 3 (Serabyn et al. 1993) and C 18 O (Wilking et al. 1993) results. The positional of the IRAS source and the NH 3 emission maximum, along with the fact that the IRAS source displays a rising spectrum from 12 to 100 μm and that it is associated with millimeter continuum emission, suggest that the IRAS source is a very young object deeply embedded in the high density gas. There are two other IRAS sources in the region, but they are not associated with high-density gas (see Fig. 2.42). At present, little is known

140 104 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.42: Same as Fig.2.7, but for the IC 1396E region. The NH 3 lowest contour level is 0.2 K and the increment is 0.15 K. The map of the CO bipolar outflow is from Wilking et al. (1990) about these sources. All the near-ir sources detected in the region appear projected on the high density gas, indicating the young nature of these objects. The outflow axis is oriented at a position angle of 75, almost perpendicular to the dense core we have mapped. The kinetic temperature derived for this region, 19 K, is one of the largest of our sample. Serabyn et al. (1993) from their NH 3 observations (with 40 angular resolution) concluded that the temperature increases outware from the center, from a value of 17 K to a 26 on the surface, suggesting that the clump is heated externally.

141 2.3. Results HHL 73 HHL 73 is an Herbig-Haro like object, whose position coincides, within observational errors, with an H 2 O maser (Gyulbudaghian et al. 1987) and with the source IRAS A region of 9 7 around HHL 73 was mapped in ammonia by Verdes-Montenegro et al. (1989), using also the Haystack radio telescope. Their observations revealed a condensation with an angular size of , elongated in the NW-SE direction, and with the HHL 73 object located very close to the ammonia emission peak. Verdes-Montenegro et al. (1989) detected also a weaker ammonia condensation, located 5 northeast of the main condensation. No signs of star formation associated with this second clump are known at present. The region was mapped in CS by Pastor et al. (1991). The CS emitting region is elongated in the E-W direction and it is more extended (23 7 ) than the region mapped in ammonia by Verdes-Montenegro et al. (1989). The CS structure presents several emission peaks, three of them coinciding with IRAS , IRAS and IRAS These IRAS sources have faint optical counterparts on the Palomar Sky Survey red print and were classified as protostar type by Dobashi et al Dobashi et al. (1993) have detected three highly asymmetric molecular outflows associated with these IRAS sources. To complete the study in NH 3 of this region, we carried out new observations, completing those of Verdes-Montenegro et al. (1989), in order to cover the overall region observed in CS. In Fig we show the complete NH 3 map of the region (including the data of Verdes-Montenegro et al. 1989). Four ammonia clumps, coinciding with emission peaks in the CS map of Pastor et al. (1991), are observed in the figure. Three of the ammonia clumps are associated with an IRAS source, located very close to the emission peak, thus suggesting that these clumps contain a young embedded object. The mean separation between these clumps ( 1 2 pc) is of the order of the typical distance between stars. Therefore, this region appears to be an example of simultaneous formation of several stars in the same cloud, as it was suggested by Pastor et al. (1991).

142 106 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.43: Same as Fig. 2.7, for the HHL 73 region. The ammonia lowest contour level is 0.12 K, and the increment is 0.1 K. The NH 3 map obtained by Verdes-Montenegro et al. (1989) is also included. The maps of the CO outflows are from Dobashi et al. (1993) L1165 L1165 is a small cloud whose distance is not well established. Estimates by different authors range from 200 pc to 750 pc. We will adopt a distance of 750 pc, based on the assumption that the cloud is part of the IC 1396 region (Schwartz et al. 1991). Parker et al. (1991) discovered a bipolar molecular outflow centered on IRAS , which was proposed as the exciting source. This IRAS source, that has a near-ir counterpart (Tapia et al. 1997), is located 15 to the NE of the reflection nebulosity GY 22 (Gyulbudaghian 1982; Reipurth et al. 1997). Reipurth et al. (1997) reported a HH object, HH 354, located 11 NE of the IRAS position and at the end of a cavity in the molecular cloud, possibly excavated by the molecular outflow. These authors proposed that HH 354, the cavity, the molecular outflow and the GY 22 nebulosity are all parts of a single giant outflow excited by the IRAS source. From near-ir spectroscopy, Reipurth & Aspin (1997) concluded that IRAS (=HH 354 IRS) is a FUor candidate. About 1. 4 north of IRAS and well off the outflow axis, lies the source IRAS , which

143 2.3. Results 107 Figure 2.44: Same as Fig. 2.7, for the L1165 region. The NH 3 lowest contour is 0.15 K and the increment is 0.05 K. The IRAS sources are, from north to south, IRAS and IRAS (=HH 354 IRS). The CO bipolar outflow is from Parker et al. (1991) also has a n-ir counterpart Tapia et al. (1997). The NH 3 map (Fig. 2.44) shows a condensation with the emission peaking very close to the position of IRAS The IRAS colours of this source are typical of embedded sources (Parker 1991) and it is surrounding by the reflection nebulosity. Altogether suggest that HH 354 IRS is a young object embedded in the high density gas. IRAS appears associated with the dense gas and located close to the emission maximum, but its IRAS colours correspond to a blackbody at T>1000 K, suggestive of background source (Tapia et al. 1997). This source needs more accurate observations in order to establish its relationship with the core and the outflow.

144 108 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.45: Same as Fig. 2.7, for the region aroud IRAS The NH 3 lowest contour is 0.2 K and the increment is 0.1 K. The CO bipolar outflow is from Dobashi et al. (1994) IRAS Dobashi et al. (1994) discovered a molecular outflow associated with the source IRAS , which is among the most luminous source in the Cepheus region. The NH 3 distribution (Fig. 2.45) shows a compact condensation with the emission maximum located at the IRAS position, in agreement with the 12 CO and 13 CO maps obtained by Dobashi et al. (1994). The source exhibits a rising spectral energy distribution towards longer wavelenghts. This fact, along with its association with high density gas, suggest that IRAS is a very young stellar object, maybe a protostar as suggested by Dobashi et al. (1994).

145 2.3. Results L1221 L1221 is a small isolated dark cloud associated with IRAS , which has an energy distribution rising to longer wavelenghts. Umemoto et al. (1991) discovered a bipolar molecular outflow centered near the IRAS source, which has been proposed as the outflow exciting source. The outflow shows a U-shaped structure open to the northwest. Alten et al. (1997) discovered a HH object, HH 363, in the vicinity of the IRAS source. Anglada et al. (2001) detected three cm continuum sources in this region, but none seems to be related with the IRAS source. The NH 3 emission (Fig. 2.46) is distributed in a compact condensation centered on the IRAS source, with weaker emission extending to the NE. The emission peak coincides with the IRAS position. Umemoto et al. (1991) have mapped this region using other molecules high density tracers (CS, HCO +,HCNandC 18 O). The size of the NH 3 condensation (see Table 2.7) is similar to that obtained in CS and HCO +, but the emission peaks of the CS, HCO +, and HCN cores are located 54 ( 0.06 pc) to the south of the NH 3 emission peak. A displacement between the CS and NH 3 emission peaks has been found in several other regions, and has been interpreted by Morata et al. (1997) in terms of chemical evolution. Our data favor IRAS as the exciting source of the outflow, in opposite to the proposal of Umemototo et al. (1991), who proposed that an object located to the south at the position of the CS emission peak will be the driving source L1251 L1251 is an elongated dark cloud (Lynds 1962) apparently belonging to the Cepheus Flare giant molecular cloud complex (Lebrun 1986). The estimated distance of this cloud is between 200 pc to 500 pc. We have adopted a distance of 300 pc, estimated from a photometric study by Kun & Prusti (1993). Several indications of low-mass star formation have been found in L1251, with several Hα emission stars and infrared point sources detected in the cloud (see Kun & Prusti 1993 and references therein). Our following study of this region focuses on two IRAS sources, IRAS and IRAS , which are the most luminous sources in L1251 and appear to be the powering sources of bipolar CO outflows.

146 110 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.46: Same as Fig. 2.7, for the L1221 region. The NH 3 lowest contour level is 0.25 K and the increment is 0.2 K. The map of the CO bipolar outflow is from Umemoto et al. (1991) IRAS IRAS is the driving source of an extended and poorly collimated outflow, L1251-A (Schwartz et al. 1988; Sato & Fukui 1989). The outflow map differs from one study to the other. The outflow map obtained by Sato & Fukui (1989) represents molecular gas with relatively low velocity ( < 4kms 1 ) and is extended ( 1.1 pc), with the axis approximately in the NE-SW direction. On the other hand, the map obtained by Schwartz et al. (1988), with higher angular resolution, includes higher velocity gas ( < 8kms 1 ), is more compact and shows a clear asymmetry in the intensity the two lobes. Balázs et al. (1992) detected several Herbig-Haro objects (apparently forming an optical jet with its axis coincident with that of the CO outflow), and propose

147 2.3. Results 111 Figure 2.47: Same as Fig. 2.7, for the IRAS region in L1251. The ammonia lowest contour level is 0.1 K, and the increment is 0.1 K. that the exciting source of these objects is also IRAS Anglada et al. (1996) have detected this source in the radio continuum at 3.6 cm. Xiang & Turner (1995) have detected an H 2 Omaserwithin 0. 6 of the IRAS position. The source IRAS (probably a T Tauri star; Kun & Prusti 1993) lies about 2 to the north-east of IRAS In Fig. 2.47, we show our ammonia map. The two IRAS sources lie at the edge of the NH 3 condensation, being displaced by 2 ( 0.1 pc) from the emission peak. At present, no source coincident with the ammonia emission peak has been found. As the emission peak is displaced from the outflow center, it is not likely

148 112 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.48: Same as Fig. 2.7, for the IRAS region in L1251. The lowest contour level is 0.15 K, and the increment is 0.1 K. that the outflow exciting source coincides with this ammonia maximum. The fact that the source proposed as the exciting source of the outflow, IRAS , is displaced 0.1 pc in projection from the ammonia emission peak may be due either because the outflow has disrupted part of the cloud core, or because the source was formed in the dense cloud but has escaped out of the clump (for a velocity of the star with respect to the cloud of 1kms 1,atimeof 10 5 yr, which is similar to the time-scale of the outflow, is required to cover the observed displacement). We note that Morata et al. (1997) have mapped this region in CS, obtaining that the CS extends over a region larger than the NH 3 with IRAS near a CS emission peak. IRAS CO observations in the region associated with this source (Sato & Fukui 1989; Sato et al. 1994) have revealed a well collimated and very compact bipolar outflow, L1251- B, extending over 4 in the NW-SE direction. IRAS (L FIR =14L ;

149 2.3. Results 113 Sato et al. 1994) lies near the center of the two lobes, suggesting that is driving the bipolar outflow. IRAS , apparently without optical counterpart (Kun & Prusti 1993, Eiroa et al. 1994b), is detected in the radio continuum at 3.6 cm by Anglada et al. (1996), and is likely to be a protostar embedded in a dense molecular cloud core (Sato et al. 1994). Eiroa et al. (1994b) found several Herbig-Haro objects (HH 189A, B and C) that may be associated with IRAS or with a nearby nebulous star. Kun & Prusti (1993) and Eiroa et al. (1994b) also found several infrared sources and Hα emission stars in this region. In Fig we show our ammonia map. The observed NH 3 condensation appears to be very elongated ( 8 2 ) in the east-west direction. IRAS is located in the midst of the high density gas, confirming that it is an embedded source. However, this source is displaced 1 ( 0.1 pc)fromthenh 3 emission peak. Several other infrared sources are observed towards the NH 3 condensation, suggesting that they represent embedded sources. One of these sources coincides positionally with the NH 3 emission peak. There is a secondary emission peak (located 6 to the west of the main one) that appears not to be associated with any known infrared source. The source IRAS is located 4 to the northeast of IRAS , at the edge of the NH 3 structure, suggesting that it is not deeply embedded in the dense cloud. This source is associated positionally with an Hα emission star, and it is proposed to be a T Tauri star (Kun & Prusti 1993), in agreement with the suggestion that this source is more evolved than the sources still deeply embedded in dense gas. From our NH 3 data, we found a velocity gradient of 1.4 kms 1 pc 1 in the NE-SW direction, with sudden velocity shifts of up to 1 km s 1 (corresponding to gradients of 8 km s 1 pc 1 ) along the region. In Fig we show a positionvelocity diagram along the major axis of the clump. The velocity gradient does not follows the NH 3 condensation axis, but it has a complex bidimensional structure, so that we do not think that it is due to a global rotational motion of the dense condensation. Goodman et al. (1993) from NH 3 observations, Morata et al. (1997) from CS observations, and Sato & Fukui (1989) from C 18 O, also found the existence of a velocity gradient in this region. In Fig. 2.50, we show the overall L1251 region, enclosing the two ammonia condensations we have mapped and their associated molecular outflows and the CS map obtained by Morata et al. (1997) for this region The CS distribution is elongated

150 114 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.49: Position-velocity diagram of the NH 3 (1,1) main line along the major axis (P.A. = 0 ) of the condensation associated with IRAS , in L1251. The lower contour level is 0.2 K and the increment is 0.05 K. Right ascension offsets are from the position of IRAS in the east-west direction and englobes the two clumps detected in NH 3. The CS emission in the region near IRAS contains two local emission maxima, which are located very close to the sources IRAS and IRAS These authors noted that the NH 3 clump is located outside the main CS emission region. The CS emission is stronger in the region around IRAS The CS distribution is elongated in the southeast-northwest direction and the CS emission maximum is located 3. 2 to the north-west of the NH 3 peak. We have not detected ammonia emission at the position of the CS emission maxima. Note that the two NH 3 condensations we mapped in this region coincide with the two brightest spots in the C 18 O map by Sato et al. (1994).

151 2.3. Results 115 Figure 2.50: (top) Region enclosing the two ammonia dense cores observed in L1251 (Figs and 2.48). Superposed are shown the two associated CO outflows, L1251-A and L1251-B (solid lines indicate blueshifted gas and dashed lines indicate redshifted gas) (Sato et al. 1994). (bottom) Contour map of the CS emission in L1251 (from Morata et al. 1997) (Solid lines indicate CS emission and dashed lines indicate the NH 3 half power contour)

152 116 Chapter 2. Ammonia towards molecular and optical outflows NGC 7538 The high-density core in the NGC 7538 molecular cloud is a very active star-forming region, wich contains five infrared sources (IRS 1, 2, 3, 9 and 11) within an area of (Werner et al. 1979). Estimates of the distance of this region range from 2.2 to 4.7 kpc. We will adopt a distance of 2.7 kpc (Kameya et al. 1986). Campbell & Thompson (1984) found a large high-velocity outflow near IRS 1. Kameya et al. (1989) discovered three additional outflows in the region, two associated with IRS 9 and 11 and the third one without IR source associated. Davis et al. (1998) detected a collimated H 2 jet associated with the IRS 9 outflow, a possible bow shocks in both the IRS 1 and IRS 9 outflows, and a number of H 2 compact knots which coincide with the IRS 11 outflow, that may be related with it. Davis et al. (1989) also detected a cavity to the norhtwest of IRS1. Figure 2.51: Same as Fig. 2.7, for the NGC 7538 region. The NH 3 lowest contour level is 0.25 K and the increment is 0.2 K. The maps of the CO bipolar outflows are from Kameya et al. (1989)

153 2.3. Results 117 The NH 3 map (Fig. 2.51) shows a condensation elongated in the east-west direction, with the main peak towards the position of IRS 11, and a weaker peak near IRS 9. IRS 1-3 also appear projected towards the ammonia condensation. The association of IRS 11 with the emission peak suggest that this source is the most embedded object, in agreement with the CS observations (Kameya et al. 1986), for which the emission also peaks close to the position of IRS 11. The NH 3 line profiles show broad intrinsic line widths, with values ranging from ΔV =1.68 km s 1 to 3.41 km s 1. The broadest intrinsic line width is found very close to the IRS 11 position. Fig shows a contour map of the NH 3 intrinsic line width. The NH 3 hiperfine broadening is about 0.5 km s 1 and the thermal broadening at the derived kinetic temperature ( 28.3K,seeTable2.7)is 0.27 km s 1, both are significatively smaller than the observed broadening, that could indicates turbulent motions of the gas, or that the dense gas is accelerated by the outflows. These broadening is also observed in the CS line profiles (Kameya et al. 1986) L1262 L1262 is an isolated Bok globule with a very high visual extinction (Lynds 1962) located at a distance of 200 pc (Parker et al. 1991). Parker et al. (1988, 1991) discovered a well-collimated bipolar molecular outflow approximately 2. 5inextentalong its axis. Interferometric 12 CO observations (Terebey et al. 1989) show a more compact ( 20 ) outflow. The outflow is elongated in the northeast-southwest direction and is centered at the position of the source IRAS , which is proposed as the exciting source of the outflow. This IRAS source has been classified as a Class I embedded source without optical counterpart (Parker 1991). The velocity of the outflow decreases gradually as one moves away from the source (Parker et al. 1988). Anglada et al. (1996) found two radio continuum sources at 3.6 cm, one of them being associated with the IRAS source. Our NH 3 map is shown in Fig The NH 3 condensation presents two emission peaks, one of them coinciding with the source IRAS Our map is similar to the map obtained by Benson et al. (1984) using the same ammonia inversion line, but our sensitivity is slightly better and we are able to distinguish two emission peaks. Zhou et al. (1989) observed this region in CS, J =2 1andJ =3 2,

154 118 Chapter 2. Ammonia towards molecular and optical outflows Figure 2.52: A contour map of the NH 3 intrinsic line width for the NGC 7538 region. The lowest contour level is 1.6 km s 1 and the increment is 0.3 km s 1 obtaining that the CS emission is more extended than the NH 3 one, as it is usually found in other regions. 2.4 Discussion Location of the exciting sources of the outflows Through the (J, K) = (1,1) and (2,2) inversion transitions of the NH 3 molecule we have studied the dense gas in a sample of 53 regions with signs of star formation, as indicated by the presence of outflow activity. We have been able to detect ammonia emission in 40 regions and we have mapped 38 of them. This high rate of detections is a clear indication of the strong association between NH 3 emission and outflow activity. This result confirms the young nature of the observed objects, since they

155 2.4. Discussion 119 Figure 2.53: Same as Fig. 2.7, for the L1262 region. The ammonia lowest contour level is 0.15 K, and the increment is 0.1 K. The map of the CO outflow is from Yun & Clemens (1994). appear to be still associated with (and most of them embedded in) the dense gas from where they have been formed. In almost all cases where we have mapped the NH 3 emission associated with molecular outflows, the ammonia maximum is located near (< 0.1 pc) the position of a candidate for driving the outflow. This result gives support to their identification as the outflow exciting sources, following the criterion proposed by Anglada et al. (1989) for such identification. The region IRAS is the only one associated with molecular outflow where the NH 3 emission maximum is far ( 0.7 pc) from the position of the proposed exciting source, but closer to the center of symmetry of the outflow; for this region, we suggest that the exciting source of the outflow could be an undetected embedded object located close to the NH 3 emission maximum.

156 120 Chapter 2. Ammonia towards molecular and optical outflows For the sources of our sample that are only associated with optical signs of outflow, in general, the NH 3 emission is weak. Only in the case of the HH270/110 region, the position of the proposed exciting source (HH 270 IRS) coincides with an ammonia maximum (although it is not the strongest maximum in the region mapped). In all the other cases, there is not any known object near the ammonia maximum that can be a good candidate to drive the outflow Physical parameters of the dense cores The sizes of the condensations we have mapped in NH 3 range, in general, from 0.1 to 1 pc. A somewhat larger value of 2 pc is obtained for regions NGC 281 A-W, NGC 7538 and IRAS , the most distant sources of our sample (although the size of the IRAS region may be overestimated by an order of magnitude, since we have adopted the upper limit for the distance). We find evidence for some elongation in the condensations we have mapped (as was noted, in general, by Myers et al. 1991). However, in many regions our angular resolution is not good enough to allow us to further discuss on the morphology of the sources. In particular, we are not able to establish whether or not these condensations play a relevant role in the collimation of the outflows in these regions (as suggested, e.g., by Torrelles et al. 1983). We note, however, the very high degree of elongation of the condensation associated with IRAS in L1251, reminiscent of the NH 3 large-scale structure observed in L1448 (e.g., Anglada et al. 1989). In both cases (L1251 and L1448), several objects are seen in projection towards the elongated NH 3 structure. A high angular resolution study of the L1251 region may be relevant in order to investigate a possible fragmentation of the structure associated with IRAS A higher angular resolution study may also be relevant for other sources of our sample that appear compact in our present single-dish study. Nevertheless, some condensations present in our maps a structure with several clumps, such as L673. In particular, in both M N and IRAS , two clumps with different velocities, but gravitationaly bound, can be identified. From the values of the kinetic temperature obtained for these regions (see Table 2.2 and Table 2.7), the thermal line widths expected are 0.2 kms 1. This value is significantly smaller than the intrinsic line widths we have obtained, which range from 0.3 to 3.8 km s 1 (see Table 2.2 and Table 2.4). This result suggests

157 2.4. Discussion 121 that the star formation process probably introduces a significant perturbation in the molecular environment. The lower value for the intrinsic line width is found in the V LSR =3.8 kms 1 component of the L1641-S3 region, whose line widths are almost thermal; this result could indicate that IRAS , which is observed projected towards the center of the L1641-S3 core is associated with the V LSR =5.0 km s 1 component rather than with the V LSR =3.8 kms 1 one. The largest value of the line width is obtained for NGC 7538, which is also the region with the highest value of the mass and of the kinetic temperature of our sample. In general, we found the that the more massive regions present the larger values of the line width (see Table 2.8). Also, larger values of the line width are found for the most luminous sources. In order to quantify this possible relationship, in Fig. 2.54, we have plotted the nonthermal line width (substracting the thermal component using the derived rotational temperature of the region) and the luminosity of the associated source. We found that both parameters are related by L bol =10 2.0±0.1 ΔVnth 4.7±0.4, with a correlation coefficient of A similar correlation was found by Jijina et al. (1999). We note also that regions associated only with CO molecular outflow have, in general, larger values of the line width than regions with only optical outflow. In part due to our lack of angular resolution, we are not able to measure in detail the velocity gradient in our regions. It is remarkable that in L1287 and in the condensation associated with IRAS in L1251, our results show the presence of a strong velocity gradient with sudden velocity shifts of up to 1kms 1 between contiguous positions. In Chapter 4 we present a high angular resolution study of the L1287 region, in order to resolve the kinematics of this region. Also, a study with high angular resolution of the L1251 region appears to be very promising. The region L1641-S3 exhibits two velocity components separated by 1kms 1 that we interpret as two distinct clumps. The H 2 column densities we have obtained are cm 2 (assuming [NH 3 /H 2 ] =10 8 ), implying mean visual extinctions 10 mag. For L483 and L379 we have obtained the highest H 2 column density ( cm 2, corresponding to a visual extinction of 100 mag), suggesting that these objects are very deeply embedded. Themasseswehaveobtainedfortheobserved regions cover a wide range of values, from 1 to 3000 M (the highest value corresponds to the NGC 7538 region).

158 122 Chapter 2. Ammonia towards molecular and optical outflows log L bol (Lo) log ΔV nth (km/s) Figure 2.54: Bolometric luminosity vs. nonthermal line widht for the observed regions. Most of the sources of our sample are low-mass objects and the values of the mass obtained for their associated high-density cores are below 100 M. The values derived for the mass coincide, in general, with the virial mass within a factor of 3. This general trend suggests that most of the observed condensations are near virial equilibrium and that the assumed NH 3 abundance is adequate. Although, we have found four regions for which the derived mass exceeds the virial mass by a large factor. In particular, L483 is the region for which the calculated mass exceeds the virial mass by the largest factor ( 7). This could imply that for this source the cloud is still in the process of gravitational collapse. Myers et al. (1995) detected asymmetric line profiles in this region consistent with infall motion, according to the modeling of Anglada et al. (1987). Although the uncertainties involved are still large, it seems clear that this object is among the youngest sources in our sample, in agreement with the results of Fuller et al. (1995), which classify this as a very young object. Fuller & Wootten (2000) have recently carried out a high angular resolution ammonia study of this core with the VLA.

159 2.4. Discussion Evolutive differences in the outflow sources We have detected and mapped the NH 3 emission in 36 out of 43 regions with molecular outflow in our sample (Table 2.1 and Table 2.4). In four of the seven regions where we failed in detecting ammonia emission, the evidence for CO outflow is weak. In the 36 regions associated with molecular outflow, the NH 3 emission is usually strong; the emission is faint (T MB < 0.5 K; see Table 2.2 and Table 2.4) only in six regions (RNO 43, HH 83, IRAS , L100, V1057 Cyg, L1165), five of them with a weak CO outflow. On the other hand, in the regions without molecular outflow, the ammonia emission is usually undetectable or it is very faint. These results tentatively suggest that the ammonia emission tends to be more intense for those sources associated with molecular outflow than for the sources associated with only optical signs of outflow (such as jets and Herbig-Haro objects). In order to substantiate this possible relationship between the type of outflow and the intensity of the NH 3 emission, we have complemented the sample of regions observed in this paper with the results of other Haystack NH 3 observations reported in the literature. We have studied the distribution of the intensity of the NH 3 emission, as measured by the main beam brightness temperature towards the outflow exciting source, in this larger sample of regions. We note here that the NH 3 brightness temperature is a good measure of the intensity of the NH 3 emission only for sources that fill the beam of the telescope. For unresolved sources, a more adequate comparison should be made in terms of the distance corrected flux density of the ammonia emission ( ammonia luminosity ). As we expect that for nearby sources the angular size of the ammonia emission will be, in general, larger than the telescope beam, we have used the main beam brightness temperature to make the comparison, restricting our sample to nearby enough regions. Thus, we have used sources with D 1 kpc, and completed our sample with the data from Torrelles et al. (1983) (9 sources), Anglada et al. (1989) (13 sources), Benson & Myers (1989) (5 sources, and 2 additional sources observed at Green Bank), Verdes-Montenegro et al. (1989) (3 sources), and Persi et al. (1994) (1 source; this source is extensively discussed in Chapter 3). Our final sample is shown in Table 2.9. It contains a total of 80 sources, with 31 sources associated only with molecular outflow, 40 sources associated both with optical and molecular outflow and 9 sources with only optical outflow. In Fig we present the distribution of the NH 3 main beam brightness temperature towards

160 124 Chapter 2. Ammonia towards molecular and optical outflows the position of the proposed outflow exciting source (Table 2.9) for the three groups of sources. The mean values of the NH 3 brightness temperature are 1.31 K (only molecular outflow), 1.34 K (optical and molecular outflow) and 0.41 K (only optical outflow). Despite the relatively small number of sources with only optical outflow, it is clear that these sources tend to present lower values for the NH 3 brightness temperature, while for the sources with molecular outflow the distribution is displaced to higher values of the NH 3 brightness temperature. We conclude, thus, that the ammonia emission is in general more intense in molecular outflow sources than in sources with optical outflow. We should note that recent sensitive studies have detected weak CO outflows in regions where previous studies failed in the detection (e.g., in HH 1-2 or HH 34; Chernin & Masson 1995). We have not attempted to take into account the effect of the intensity of the molecular outflow in our study, and we have only considered whether or not an outflow detection has been reported in a given region. The fact that the sources of molecular outflow present more intense ammonia emission can be interpreted as indicating that these sources are deeply embedded in the high density gas, and surrounded by a larger amount of molecular gas, while those sources with only optical outflow have already dispersed the molecular core or escaped from it. This interpretation can be corroborated by comparing the estimated column density in the sources listed in Table 2.9. We found that the ammonia column density towards the outflow exciting source decreases as the outflow activity becomes prominent in the optical. The mean values of the NH 3 column density are cm 2 (only molecular outflow), cm 2 (optical and molecular outflow) and cm 2 (only optical outflow). In Fig we show the distribution of the NH 3 column density for the three groups of sources. A similar correlation is obtained if the comparison is made in terms of the estimated mass of the associated core, but in this last case it is unclear to what extent should the NH 3 emission be considered as associated with a given object. These results suggest an evolutive sequence of the sources, traced by the intensity of the ammonia emission and the observational appearance of the outflow. Molecular and optical outflow would be phenomena that dominate, observationally, at different stages of the early stellar evolution. In the younger objects molecular outflows will be prominent, while optical outflows will progressively show up as the star evolves. However, this result does not exclude that both phenomena could

161 2.4. Discussion 125 Table 2.9: Regions associated with molecular or optical outflow observed in NH 3 a Source Outflow Ref. b T MB N(NH 3 ) c Ref. D Ref. associated (K) (10 14 cm 2 ) (pc) M N (IRAS ) CO M S (IRAS ) CO L1287 CO L1293 CO L1448 IRS1 CO, HH 72, L1448 IRS2 CO, HH L1448 IRS3 CO, HH 23, L1448 C CO, HH 23, GL490 CO 6» 0:5» 0: L1455 IRS1 CO, HH 9, L1455 IRS2 CO, HH 9, L1489 CO, HH 10, HH 156 HH 1» 0:2» 0: HH 159 CO, HH 1» 0:4» 0: HH 158 HH 1» 0:3» 0: HH 31 CO?,HH L1524 (Haro 6-10) CO, HH 73, 14» 0:6» L1551 IRS 5 CO, HH 15, HL Tau CO, HH 17, 18» 1» L1551 NE CO, HH L1642 CO, HH 1» 0:1» 0: L1527 CO, HH 20,74, L1634 (IRAS ) CO, HH L1634 (IRS 7) CO, HH 83, RNO 43 (IRAS ) CO, HH 21, HH 83 CO, HH 26, HH 84 HH HH 33/40 HH 27» 0:3» 0: HH 86/87/88 HH 25» 0:2» 0: HH 34 CO, HH 30, L1641-N CO, HH 32, HH HH 27» 0:5» 0: Haro FIR CO L1641-S3(high velocity) CO HH 68 HH 1» 0:3» 0: B35 CO HH 26 IR CO, HH 36, HH 25 MMS CO, HH 75, NGC 2071 CO

162 126 Chapter 2. Ammonia towards molecular and optical outflows Table 2.9: Continued Source Outflow Ref. b T MB N(NH 3 ) c Ref. D Ref. associated (K) (10 14 cm 2 ) (pc) HH 270 IRS HH IRAS CO HH 111 CO, HH Mon R2 CO Mon R2-N CO GGD CO RMon CO, HH 40, 35» 0:5» 0: NGC2264(HH14-4/5/6) HH 41» 1» HH 120 CO, HH 43,77, L1709 CO 1» 0:4» 0: L43 CO L100 CO L483 CO L588 CO, HH RCrA(HH 100-IR) CO, HH 72,50, RCrA(IRS 7) CO, HH 72,50, L673 CO : CB 188 CO 1» 0:2» 0: HH 32a CO, HH 17,35» 0:6» 0: L778 CO B335 CO, HH 53, L797 CO 1» 0:2» 0: IRAS CO V1057 Cyg CO L1228 CO, HH 55, V1331 Cyg CO, HH 72, L1172 CO CB 232 CO IC 1396 E CO NGC 7129 CO, HH 58, HHL73 (IRAS ) CO HHL73 (IRAS ) CO,HHL,HH 60,61, HHL73 (IRAS ) CO : L1165 CO,HH IRAS CO S140N (IRAS ) CO S140N (Star 2) CO, HH 82,

163 2.4. Discussion 127 Table 2.9: Continued Source Outflow Ref. b T MB N(NH 3 ) c Ref. D Ref. associated (K) (10 14 cm 2 ) (pc) L1221 CO, HH L1251 (IRAS ) CO, HH 64, L1251 (IRAS ) CO, HH 64, L1262 CO : a Regions with distance» 1 kpc. b Main brightness temperature at the position of the suspected exciting source. c Lower limit of the beam-averaged column density at the position of the suspected exciting source. References: (1) see Table 2.3; (2) this chapter; (3) Herbig & Jones 1983; (4) Anglada et al. 1989; (5) Eiroa et al. 1994a; (6) Snell et al. 1984; (7) Torrelles et al. 1983; (8) Fukui et al. 1993; (9) Goldsmith et al. 1984; (10) Myers et al. 1988; (11) Benson & Myers 1989; (12) Strom et al. 1986; (13) Reipurth 1994; (14) Elias 1978; (15) Snell et al. 1980; (16) Mundt & Fried 1983; (17) Edwards & Snell 1982; (18) Mundt et al. 1988; (19) Eiroa et al. 1994a; (20) Heyer et al. 1987; (21) Edwards & Snell 1984; (22) Jones et al. 1984; (23) Bachiller et al. 1990; (24) Maddalena & Morris 1987; (25) Reipurth 1989; (26) Bally et al. 1994; (27) Haro 1953; (28) Verdes-Montenegro et al. 1989; (29) Haro 1959; (30) Chernin & Masson 1995; (31) Genzel et al. 1981; (32) Fukui et al. 1986; (33) Chen et al. 1993; (34) Felli et al. 1992; (35) Herbig 1974; (36) Snell & Edwards 1982; (37) Bally 1982; (38) Loren 1981; (39) Rodr guez et al. 1982; (40) Cantó et al. 1981; (41) Adams et al. 1979; (42) Cohen & Schwartz 1987; (43) Olberg et al. 1989; (44) Persi et al. 1994(see also Chapter 3); (45) Petterson 1984; (46) Chini 1981; (47) Parker et al. 1988; (48) Reipurth & Gee 1986; (49) Ladd et al. 1991a; (50) Strom et al. 1974; (51) Marraco & Rydgren 1981; (52) Armstrong & Winnewisser 1989; (53) Frerking & Langer 1982; (54) Vrba et al. 1986; (55) Haikala & Laureijs 1989; (56) Bally et al. 1995; (57) Chavarr a-k 1981; (58) Loren 1977; (59) Ray et al. 1990; (60) Dobashi et al. 1993; (61) Gyulbudaghian et al. 1987; (62) Eiroa et al. 1993; (63) Crampton & Fisher 1974; (64) Sato & Fukui 1989; (65) Balázs et al. 1992; (66) Kun & Prusti 1993; (67) Eiroa et al. 1994b; (68) Parker et al. 1991; (69) Reipurth et al. 1998; (70) Bally et al. 1997; (71) Gómez et al. 1997; (72) Levreault 1985; (73) Hogerheijde et al. 1998; (74) Tamura et al. (1996); (75) Gibb & Davis 1998; (76) Tafalla et al. 1997; (77) Nielsen et al. 1998; (78) Anderson et al. 1997; (79) Whittet et al. 1996; (80) Mundt & Eislöffel 1998; (81) Devine, Reipurth & Bally 1997; (82) Davis et al. 1998; (83) Davis et al. 1997; (84) Hoddap & Ladd 1995.

164 128 Chapter 2. Ammonia towards molecular and optical outflows NUMBER OF SOURCES CO outflow HH & CO outflow HH outflow log T MB (K) Figure 2.55: Distribution of the NH 3 main beam brightness temperature for sources with only molecular outflow (top), for sources with both molecular and optical outflow (middle), and for sources with only optical outflow (bottom).

165 2.4. Discussion 129 NUMBER OF SOURCES CO outflow HH & CO outflow HH outflow log N (NH 3 ) (cm 2 ) Figure 2.56: Distribution of the NH 3 column density for sources with only molecular outflow (top), for sources with both molecular and optical outflow (middle), and for sources with only optical outflow (bottom).

166 130 Chapter 2. Ammonia towards molecular and optical outflows coexist simultaneously as is required in the so-called unified models, in which molecular outflows are driven by highly collimated jets (e.g., Raga et al. 1993); only the observational appearance of the outflow evolves in time as the star loses progressively the surrounding high density gas. In this scenario, the driving optical jet is becoming visible as a consequence of the ambient molecular material being progressively removed by the effect of the molecular outflow itself. Alternatively, the observed differences could represent intrinsic differences in the amount of molecular high density gas from one to another region. 2.5 Conclusions We have detected the ammonia emission in 40 sources of a sample of 53 sources associated with molecular and/or optical outflows and we have mapped 38 of them. In addition, we have searched for H 2 O maser emission towards 15 regions, and detected a weak H 2 O maser in three of them, HH 265, AFGL 5173 and IRAS Our main conclusions drawn from this study can be summarized as follows: 1. In all the molecular outflow regions we have mapped, the NH 3 emission peak is very close to the position of a good candidate for the outflow exciting source. 2. For two regions with only optical outflow (HH 84 and HH 86/87/88), no object is detected towards the observed (weak) NH 3 condensations, suggesting a non local origin for the flow excitation. 3. We found that, in general, the NH 3 condensations are very cold, with line widths dominated by non thermal (turbulent) motions. Among the observed sources, the more massive regions appear to produce a larger perturbation in their molecular high density environment. In general, the more luminous objects are associated with broader ammonia lines. A correlation between the nonthermal component of the line width and the luminosity of the associated object (L bol =10 2.0±0.1 ΔVnth 4.7±0.4 ) has been found. 4. The ammonia condensations appear to be, in general, close to virial equilibrium. L483 is remarkable in being associated with the largest visual extinction of our sample and being in a possible gravitational collapse, making this source a very good candidate to be a very young deeply embedded object.

167 2.5. Conclusions A very elongated NH 3 structure, apparently associated with several young objects and with strong velocity gradients, has been found near IRAS in L1251. A strong velocity gradient is also found in L1287. Evidence for disruption of the L1228 NH 3 core has also been found. 6. In several regions the ammonia structure presents more than one clump. In the M N and IRAS regions, two clumps with different velocities, but gravitationally bound have been identief. 7. Our main result is the discovery of a correlation between the intensity of the NH 3 emission and the presence of molecular or optical outflow. The NH 3 brightness temperature and column density decrease as the outflow activity becomes prominent in the optical. This result suggests an evolutive scheme in which young objects lose progressively their neighboring high density gas.

168 132 Chapter 2. Ammonia towards molecular and optical outflows

169 Bibliography André, P., 1996, Mem. Soc. Astron. It., 67, 901 Adams, M.T., Strom, K.M., Strom, S.E. 1979, ApJ, 230, L183 Afonso, J.M., Yun, J.L., Clemens, D.P., 1998, AJ, 115, 1111 Akabane, K., Tsunekawa, S., Inoue, M. et al. 1992, PASJ, 44, 421 Alten, V. P., Bally, J., Devine, D, Miller, G. J. 1997, in Low Mass Star Formation - from Infall to Outflow, poster proceedings of IAU Symp. No. 182, eds. F. Malbet & A. Castets, p. 51 Alves, J.F. 1995, Master Thesis, University of Lisbon Alves, J.F., Yun. J.L. 1995, ApJ, 438, L107 Alves, J.F., Hartmann, L., Briceño, C., Lada, C.J. 1997, AJ, 113, 1395 Anderson, I.M., Harju, J., Knee, L.B.G., Haikala, L.K. 1997, A&A, 321, 575 André, P., Ward-Thompson, D., Barsony, M. 1993, ApJ, 406, 122 Anglada, G., Estalella, R., Rodríguez, L.F., Cantó, J., López, R. 1987, A&A, 186, 280. Anglada, G., Rodríguez, L.F., Torrelles, J.M., et al. 1989, ApJ, 341, 208 Anglada, G., Rodríguez, L.F., Cantó, J., Estalella, R., Torrelles, J.M. 1992, ApJ, 395, 494 Anglada, G., Rodríguez, L.F., Girart, J.M., Estalella, R.,Torrelles, J.M. 1994, ApJ, 420,

170 134 BIBLIOGRAPHY Anglada, G., Estalella, R., Mauersberger, R., et al. 1995, ApJ, 443, 682 Anglada, G., Sepúlveda, I., Gómez, J.F. 1997, A&AS, 121, 255 Anglada, G., Rodríguez, L.F., Torrelles, J.M. 1998a, ASPC, 132, 303 Anglada, G., Villuendas, E., Estalella, R. et al. 1998b, AJ, 116, 2953 Anglada, G. et al. 2001, in preparation Armstrong, J.T., Winnewisser, G. 1989, A&A, 210, 373 Bachiller, R., Cernicharo, J. 1986, A&A, 168, 262 Bachiller, R., Cernicharo, J., Martín-Pintado, J., Tafalla, M., Lazareff, B. 1990, A&A, 231, 174 Bachiller, R., Fuente, A., Tafalla, M. 1995, ApJ, 445, L51 Balázs, L.G., Eislöffel, J., Kelemen, J., Kun, M. 1992, A&A, 255, 281 Bally, J. 1982, ApJ, 261, 558 Bally, J., Devine, D. 1994, ApJ, 428, L65 Bally, J., Langer, W.D., Stark, A.A., Wilson, R.W. 1987, ApJ, 312, L45 Bally, J., Castets, A., Duvert, G. 1994, ApJ, 423, 310 Bally, J., Devine, D., Fesen, R.A., Lane, A.P. 1995, ApJ, 454, 345 Bally, J., Devine, D., Alten, V. 1997, ApJ, 478, 603 Beltrán, M.T., Estalella, R, Anglada, G, Rodríguez, L.F., Torrelles, J.M., 2001a, AJ, 121, 1556 Beltrán, M.T., Estalella, R., Ho, P.T.P, Calvet, N., Anglada, G., Sepúlveda, I., 2001b, submitted Bence, S.J., Richer, J.S., Padman, R. 1996, MNRAS, 279, 886 Benson, P.J., Myers, P.C. 1989, ApJS, 71, 89 Benson, P.J., Myers, P.C., Wright, E.L. 1984, ApJ, 279, L27

171 BIBLIOGRAPHY 135 Berrilli, F., Ceccarelli, C., Liseau, R., Lorenzetti, D., Saraceno, P., Spinoglio, L., 1989 MNRAS, 239, 255 Blitz, L., Fich, M., Stark, A.A. 1982, ApJS, 49, 183 Brand, J., Cesaroni, R., Caselli, P. et al. 1994, A&AS, 103, 541 Cabrit, S., Goldsmith, P.F., Snell, R.L. 1988, ApJ, 334, 196 Campbell, B., Thompson, R.I. 1984, ApJ, 279, 650 Cantó, J., Rodríguez, L.F., Barral, J.F., Carral, P. 1981, ApJ, 244, 102 Cao, Y.X., Zeng, Q., Deguchi, S., Kameya, O., Kaifu, N., 1993, AJ, 105, 1027 Carpenter, J.M., Snell, R.L., Schloerb, F.P. 1990, ApJ, 362, 147 Carpenter, J.M., Snell, R.L., Schloerb, F.P. 1995, ApJ, 450, 201 Carpenter, J.M., Snell, R.L., Schloerb, F.P., Skrutskie, M.F. 1993, ApJ, 407, 657 Cesaroni, R., Walmsley, C.M., Koempe, C., Churchwell, E. 1991, A&A, 252, 278 Cesaroni, R., Felli, M., Walmsley, C.M. 1999, A&AS, 136, 333 Cernicharo, J., Neri, R., Reipurth, B. 1997, in Herbig-Haro Flows and the Birth of Low Mass Stars, IAU Sym No.182, eds. B. Reipurth and C. Bertout, p. 141 Chavarría-K, C. 1981, A&A, 101, 105 Chen, H., Fukui, Y., Yang, J. 1992, ApJ, 398, 544 Chen, H., Tokunaga, T., Strom, K.M., Hodapp, K.-W. 1993, ApJ, 407, 639 Chen, H., Tokunaga, A.T. 1994, ApJS, 90, 149 Chen, H., Myers, P.C., Ladd, E.F., Wood, D.O.S. 1995, ApJ, 455, 377 Chen, H., Zhao, J.H., Ohashi, N. 1995, ApJ, 450, L71 Chen, H., Tafalla, M., Greene, T.P., Myers, P.C., Wilner, D.J., 1997, ApJ, 475, 163 Chernin, L. M., Masson, C.L. 1995, ApJ, 443, 181 Chini, R. 1981, A&A, 99,346

172 136 BIBLIOGRAPHY Chini, R., Reipurth, B., Sievers, A. et al. 1997, A&A, 325, 542 Choi, M., Panis, J.-F., Evans, N.J.II 1999, ApJS, 122,519 Claussen, M.J., Wilking, B.A., Benson, P.J. et al. 1996, ApJS, 106, 111 Clemens, D.P., Barvainis, R. 1988, ApJS, 68, 257 Codella, C., Palumbo, G.G.C., Pareshi, G. et al. 1995, MNRAS, 276, 57 Codella, C., Felli, M., Natale, V. 1996, A&A, 311, 971 Codella, C., Scappini, F. 1998, MNRAS, 298, 1092 Cohen, M. 1980, AJ, 85, 29 Cohen, M., Schwartz, R.D. 1983, ApJ, 265, 877 Cohen. M., Harvey, P.M.,Schwartz, R.D. 1985, ApJ, 296, 633 Cohen, M., Schwartz, R.D. 1987, ApJ, 316, 311 Crampton, D. & Fisher, W.A. 1974, Pub. Dominion Ap. Obs., 14, 283 Curiel S., Raymond J.C., Rodríguez L.F., Cantó J., Moran J.M., 1990, ApJ, 365, L85 Davis, C.J., Mundt, R., Eislöffel, J. 1994, ApJ, 437, L55 Davis, C.J., Ray, T.P., Eislöffel, J., Corcoran, D. 1997, A&A, 324, 263 Davis, C.J., Moriarty-Schieven, G., Eislöffel, J., Hoare, M.G., Ray, T.P. 1998, AJ, 115, 1118 Dent, W.R.F., Matthews, H.E., Ward-Thompson, D. 1998, MNRAS, 301, 1049 Devine, D., Reipurth, B., Bally, J. 1997, in Low Mass Star Formation - from Infall to Outflow, poster proceedings of IAU Symp. No. 182, eds. F. Malbet & A. Castets, p. 91 Devine, D., Reipurth, B., Bally, J. 1999, AJ, 118, 972 Di Francesco, J., Evans II, N.J., Harvey, P.M., Mundy, L.G., Butner, H.M. 1998, ApJ, 509,324 Dobashi, K., Yonekura, Y., Mizuno, A., Fukui, Y. 1992, AJ, 104, 1525

173 BIBLIOGRAPHY 137 Dobashi, K., Onishi, T., Iwata, T., et al. 1993, AJ, 105, 1487 Dobashi, K., Nozawa, S., Hayashi, Y., Sato, F., Fukui, Y. 1994, AJ, 107, 2148 Eiroa, C., Lenzen, R., Miranda, L.F. et al. 1993, AJ, 106, 613 Eiroa, C., Miranda, L.F., Anglada, G., Estalella, R., Torrelles, J.M. 1994a, A&A, 283, 973 Eiroa, C., Torrelles, J.M., Miranda, L.F., Anglada, G., Estalella, R. 1994b, A&AS, 108, 73 Edwards, S., Snell, R.L. 1982, ApJ, 261, 151 Edwards, S., Snell, R.L. 1984, ApJ, 281, 237. Elias, J.H. 1978, ApJ, 224, 857 Emerson, J.P. 1987, in Star Forming Regions, IAU Symp 115, p. 19 Estalella, R., Mausberger, R., Torrelles, J.M. et al. 1993, ApJ, 419, 698 Evans II, N.J., Balkum, S., Levreault, R. M., Hartmann L., Kenyon. S. 1994, ApJ, 424, 793 Felli, M., Palagi, F., Tofani, G. 1992, A&A, 255, 293 Fiebig, D. 1995, A&A, 298, 207 Fiebig, D. 1997, A&A, 327, 758 Fiebig, D., Duschl, W.J., Menten, K.M., Tscharnuter, W.M. 1996, A&A, 310, 199 Frerking, M.A., Langer, W.D. 1982, ApJ, 256, 523 Fukui, Y. 1989, in Low Mass Star Formation and Pre-Main Sequence Objects, ed. B. Reipurth (Garching: ESO), 95 Fukui, Y., Sugitani, K., Takaba, H., et al. 1986, ApJ, 311, L85 Fukui, Y., Takaba, H., Iwata, T., Mizuno, A. 1988, ApJ, 325, L13 Fukui, Y., Iwata, T., Mizuno, A., Bally, J., Lane, P. 1993, in Protostars and Planets III, eds. E.H. Levy & J.I. Lunine (Tucson: Univ. of Arizona Press), 603 Fuller, G.A., Myers, P.C. 1993, ApJ, 418, 273

174 138 BIBLIOGRAPHY Fuller, G.A., Lada, E.A., Masson, C.R., Myers, P.C. 1995, ApJ, 453, 754 Garnavich, P.M., Noriega-Crespo, A., Green, P.J. 1992, Rev. Mex. Astron. Astrofis. 24, 99 Garnavich, P.M., Noriega-Crespo, A., Raga, A.C., Bohm, K-H. 1997, ApJ, 490, 752 Genzel, R., Downes, D. 1977, A&AS, 30, 145 Genzel, R., Reid, M.J., Moran, J.M., Downes, D. 1981, ApJ, 286, 599 Gredel, R., Reipurth, B. 1993, ApJ, 407, L29 Greene, T.P., Lada, C.J. 1997, AJ, 114, 2517 Gregersen, E. M., Evans, N.J.II, Zhou, S., Choi, M. 1997, ApJ, 484, 256 Goldsmith, P.F., Snell, R.L., Hemeon-Heyer, M., Langer, W.D. 1984, ApJ, 286, 599 Gómez, M., Whitney, B.A., Kenyon, S.J. 1997, AJ, 114, 1138 Goodman, A.A., Benson, P.C., Fuller, G.A., Myers, P.C. 1993, ApJ, 406, 528 Gyulbudaghian, A.L., Glushkov, Yu.I., Denisyuk, E.K. 1978, ApJ, 224, L137 Gyulbudaghian, A.L. 1982, PAZh, 8, 232 Gyulbudaghian, A.L., Rodríguez, L.F., Mendoza-Torres, E. 1987, Rev. Mex. Astron. Astrofis., 15, 53. Haikala, L.K., Laureijs, R.J. 1989, A&A, 223, 287 Haikala, L.F., Miller, M., Gierens, K., Winnewisser, G. 1991, in Molecular Clouds, eds. R. A. James & T. J. Millar (Cambridge: Cambridge Univ. Press), 25 Han, F., Mao, R.Q., Lu, J. et al. 1998, A&AS, 127, 181 Harju, J., Walmsley, C.M., Wouterloot, J.G.A. 1991, A&A, 245, 643 Harju, J., Walmsley, C.M., Wouterloot, J.G.A. 1993, A&AS, 98, Haro, G., 1953, ApJ, 117, 73 Haro, G., 1959, private communication to G.H. Herbig

175 BIBLIOGRAPHY 139 Hayashi, M., Hasegawa, T., Ohashi, N., Kazuyoshi, 1994, ApJ, 426, 234 Henning, Th., Cesaroni, R., Walmsley, M., Pfau, W. 1992, A&AS, 93, 525 Henning, Th., Martin, K., Reimann, H.-G., et al. 1994, A&A, 288, 282 Herbig, G.H. 1974, Lick Obs. Bull. No. 658 Herbig, G.H. 1977, ApJ, 217, 693 Herbig, G.H., Jones B.F. 1983, AJ, 88, 1040 Heyer, M.H., Snell, R.L., Goldsmith, P.F., Myers, P.C. 1987, ApJ, 321, 370 Hilton, J., White, G.J., Rainey, R., Cronin, N.J. 1986, A&A, 154, 274 Ho, P.T.P., Townes, C.H. 1983, ARA&A, 21, 231 Hoddap, K-W., Ladd, E.F. 1995, ApJ, 453, 715 Hogerheijde, M.R., van Dishoeck, E.F., Blake G.A., van Langevelde, H.J. 1998, ApJ, 502,315 Huard, T.L., Sandell, G., Weintraub, D.A. 1999, ApJ, 526, 833 Hughes, V.A., MacLeod, G.C. 1994, ApJ, 427, 857 Jones, B.F., Cohen, M., Sirk, M., Jarret, R. 1984, AJ, 89, 1404 Kameya, O., Hasegawa. T.I., Hirano, N. et al. 1986, PASJ, 38,793 Kameya, O., Hasegawa, T.I., Hirano, N., Takakubo, K., Seki, M. 1989, ApJ, 339, 222 Kameya, O., Morita, K-I., Kawabe, R., Ishiguro, M. 1990, ApJ, 355, 562 Kelly, M.L., Macdonald, G.H. 1995, Ap&SS, 224, 497 Kelly, M.L., Macdonald, G.H. 1996, MNRAS, 282, 401 Kenyon, S.J. 1999, in The Origin of Stars and Planetary Systems. Eds. C.J. Lada & N.D. Kylafis, Kluwer Academic Publishers, p. 613 Kenyon, S.J., Hartmann, L.W. 1991, ApJ, 383, 664

176 140 BIBLIOGRAPHY Kenyon, S.J., Hartmann, L., Gómez, M., Carr, J.S., Tokunaga, A. 1993, AJ, 105, 1505 Kun, M., Prusti, T. 1993, A&A, 272, 235 Lada, C.J. 1985, ARA&A, 23, 267 Lada, C.J. 1991, in Star Forming Regions, IAU Symp. No. 115, eds. M. Peimbert & J. Jugaku, (Reidel, Dordrecht), p. 1 Ladd, E.F., Adams, F.D., Casey, S., et al. 1991a, ApJ, 366, 203 Ladd, E.F., Adams, F.D., Casey, S., et al. 1991b, ApJ, 382, 555 Larionov, G.M., Val tts, I.E., Winnberg, A., Johansson, L.E.B., Booth, R.S., Golubev, V.V., 1999, A&AS, 139, 257 Launhardt, R., Henning, Th. 1997, A&A, 326, 329 Launhardt, R., Ward-Thompson, D., Henning, Th. 1997,MNRAS, 288, L45 Launhardt, R., Evans II, N.J., Wang, Y., Clemens, D.P., Henning, Th., Yun, J.L. 1998, ApJS, 119, 59 Lee, C.-F, Mundy, L.G., Reipurth, B., Ostriker, E.C., Stone, J.M., 2000, ApJ, 542, 925 Lebrun, F. 1986, ApJ, 306, 16 Levreault, R.M. 1985, Ph.D. Thesis, University of Texas at Austin Levreault, R.M. 1988, ApJS, 67, 283 Liljeström, T. 1991, A&A, 244, 483 Liljeström, T., Mattila, K., Friberg, P. 1989, A&A, 210, 337 Little, L.T., Bergman, P., Cunningham, C.T., et al. 1988, A&A, 205, 129 Lynds, B.T. 1962, ApJS, 7, 1 Loren, R.B. 1977, ApJ, 218, 716 Loren, R.B. 1981, ApJ, 249, 550 Maddalena, R.J., Morris, M. 1987, ApJ, 323, 179

177 BIBLIOGRAPHY 141 Maddalena, R.J., Morris, M., Moscowitz, J., Thaddeus, P. 1986, ApJ, 303, 375 Magnier, E.A., Volp, A.W., Laan, K., van den Ancker, M.E., Waters, L.B.F.M., 1999 A&A, 352, 228 Marraco, H.G., Rydgren, A.E. 1981, AJ, 86, 62 McCutcheon, W.H., Sato, T., Purton, C.R., Matthews, H.E., Dewdney, P.E. 1995, AJ, 110, 1762 McMuldroch, S., Blake, G.A., Sargent, A.I. 1995, AJ, 110, 354 McMullin, J.P., Mundy, L.G., Blake, G.A. 1994, ApJ, 137,305 Megeath, S.T., Wilson, T.L., 1997, AJ, 114, 1106 Minchin, N.R., Murray, A.G., 1994, A&A, 286, 579 Mitchell, G.F., Hasewaga, T.I., Dent, W.R.F., Matthews, H.E. 1994, ApJ, 436, L177 Molinari, S., Liseau, R., Lorenzetti, D. 1993, A&AS, 101,59 Moneti, A., Reipurth, B., 1995, A&A, 301, 721 Mookerjea, B., Ghosh, S.K., Karnik, A.D., Rengarajan, T.N., Tandon, S.N., Verma, R.P., 1999, ApJ, 522, 285 Morata, O., Estalella, R., López, R., Planesas, P. 1997, MNRAS, 292, 120 Moreira, M.C., Yun, J. L. 1995, ApJ, 454, 850 Moreira, M.C., Yun, J.L., Vázquez, R., Torrelles, J.M., 1997, AJ, 113, 137 Morgan, J.A., Bally, J. 1991, ApJ, 372, 505 Morgan, J.A., Snell, R.L., Strom, K.M. 1990, ApJ, 362, 274 Morgan, J.A., Schloerb, F.P., Snell, R.L., Bally, J. 1991, ApJ, 376, 618 Moriarty-Schieven, G.H., Wannier, P.G., Tamura, M., Keene, J., 1992, ApJ, 400, 260 Moriarty-Schieven, G.H., Wannier, P.G., Keene, J., Tamura, M. 1994, ApJ, 436, 800

178 142 BIBLIOGRAPHY Moriarty-Schieven, G.H., Butner, H.M., Wannier, P.G. 1995, ApJ, 455, L55 Motte, F., André, P., 2001 A&A, 372, 41 Mundt, R., Fried, J.W. 1983, ApJ, 274, L83 Mundt, R., Eislöffel, J. 1998, AJ, 116, 860 Mundt, R., Bührke, T., Fried, J.W. et al. 1984, A&A, 140, 17 Mundt, R., Brugel, E.W., Bührke, T. 1987, ApJ, 319, 275 Mundt, R., Ray, T.P., Bührke, T. 1988, ApJ, 333, L69 Mundt, R., Ray, T.P., Raga, A.C. 1991, A&A, 252, 740 Mundy, L.G., McMullin, J.P., Grossman, A.W., Sandell, G. 1993, Icarus, 106, 11 Myers, P.C., Heyer, M., Snell, R.L., Goldsmith, P.F. 1988, ApJ, 324, 907 Myers, P.C., Fuller, G.A., Goodman, A.A., Benson, P.J. 1991, ApJ, 376, 561 Myers, P.C., Bachiller, R., Caselli, P. et al. 1995, ApJ, 449, L65 Nakano, M., Sugitani, K., Sato, F., Ogura, K. 1994, ApJ, 423, L147 Nielsen, A.S., Olberg, M., Knude, J., Booth, R.S. 1998, A&A, 336, 329 Odenwald, S.F., Schwartz, P.R. 1993, ApJ, 405, 706 Ogura, K. 1985, in IAU Symp. 115, Star Forming Regions, eds. M. Peimbert & J. Jugaku (Dordrecht: Reidel), 341 Ogura, K., Walsch, J.R. 1991, AJ, 101, 185 Ohashi, N., Kawabe, R., Ishiguro, M., Hayashi, M., 1991, AJ, 102, 2054 Ohashi, N., Hayashi, M., Kawabe, R., Ishiguro, M. 1996, ApJ, 466, 317 Olberg, M., Reipurth, B., Booth, R.S. 1989, in The Physics and Chemistry of Interstellar Molecular Clouds, eds. G. Winnewisser & J.T. Armstrong, Lecture Notes in Physics, 331, 120 Onishi, T., Mizuno, A., Kawamura, A., Ogawa H., Fukui, Y. 1998, ApJ, 502, 296 Osterloh, M., Beckwith, S.V.W., 1995, ApJ, 439, 288

179 BIBLIOGRAPHY 143 Padgett, D.L., Brandner, W., Stapelfeld, K.R. et al. 1999, AJ, 117, 1490 Palla, F., Brand, J., Cesaroni, R., Comoretto, G., Felli, M. 1991, A&A, 246, 249 Palla, F., Cesaroni, R., Brand, J. et al. 1993, A&A, 280, 599 Parker, N.D. 1991, MNRAS, 251, 63 Parker, N.D., Padman, R., Scott, P.F., Hills, R.E. 1988, MNRAS, 234, L67 Parker, N.D., Padman, Scott, P.F. 1991, MNRAS, 252, 442 Pastor, J., Estalella, R., López, R., et al. 1991, A&A, 252, 320 Pauls, T.A., Wilson, T.L., Bieging, J.H., Martin, R.N. 1983, A&A, 124, 23 Persi, P., Ferrari-Toniolo, M., Marenzi, A.R., et al. 1994, A&A, 282, 233 Persi, P., Palagi, F., Felli, M. 1994, A&A, 291, 577 Petterson, B. 1984, A&A, 117, 183 Porras, A., Cruz-González, I., Salas, L., 2000 A&A, 361, 660 Price, S.D., Murdock, T.L., Shivanandan, K., Bowers, P.F. 1983, ApJ, 275, 125 Pudritz, R.E. 1988, in Galactic and Extragalactic Star Formation, eds. R.E. Pudritz & M. Fich (Dordrecht: Kluwer), 135 Pudritz, R.E., Norman, C.A. 1983, ApJ, 274, 677 Raga, A.C., Cantó, J., Calvet, N., Rodríguez, L.F., Torrelles, J.M. 1993, A&A, 276, 539 Ray, T.P. 1987, A&A, 171, 145 Ray, T.P., Poetzel, R., Solf, J., Mundt, R. 1990, ApJ, 357, L45 Reipurth, B. 1985, A&AS, 61, 319 Reipurth, B. 1989, Nature, 340, 42 Reipurth, B. 1989, A&A, 220, 249 Reipurth, B. 1991, in The Physics of Star Formation and Early Stellar Evolution, eds. C.J. Lada & N.D. Kylafis (Dordrecht: Kluwer), 497

180 144 BIBLIOGRAPHY Reipurth, B. 1994, A general catalogue of Herbig-Haro objects, electronically published via anon. ftp to ftp.hq.eso.org, directory /pub/catalogs/herbig-haro Reipurth, B., Gee, G. 1986, A&A, 166, 148 Reipurth, B., Graham, J.A. 1988, A&A, 202, 219 Reipurth, B., Heathcote, S. 1990, A&A, 229, 527 Reipurth, B., Olberg, M. 1991, A&A, 246, 535 Reipurth, B., Eiroa, C. 1992, A&A, 256, L1 Reipurth, B., Aspin, C. 1997, AJ, 114, 2700 Reipurth, B., Bally, J., Graham, J.A., Lane, A., Zealey, W.J. 1986, A&A, 164, 51 Reipurth, B., Chini, R., Krugel, E., Kreysa, E., Sievers, A. 1993, A&A, 273, 221 Reipurth, B., Raga, A.C., Heathcote, S. 1996, A&A, 311, 989 Reipurth, B., Bally, J., Devine, D. 1997, AJ, 114, 2708 Reipurth, B., Hartigan, P., Heathcote, S., Morse, J.A., Bally, J. 1997, AJ, 114, 757 Reipurth, B., Devine, D., Bally, J. 1998, AJ, 116, 1396 Reipurth, B., Yu, K.C., Rodríguez, L.F., Heathcote, S., Bally, J. 1999, A&A, 352, L83 Rodríguez, L.F in The Evolution of the Interstellar Medium, ed. L. Blitz, ASP Conference Series, 12, 183 Rodríguez, L.F., Hartmann, L.W., 1992, Rev.Mex.Astron.Astrofis., 24, 135 Rodríguez, L.F., Reipurth, B. 1994, A&A, 281, 882 Rodríguez, L.F., Carral, P., Ho, P.T.P., Moran, J.M. 1982, ApJ, 260, 635 Rodríguez, L.F., Haschick, A.D., Torrelles, J.M., Myers, P.C. 1987, A&A, 186, 319 Rodríguez, L.F., Anglada, G., Raga, A. 1995, ApJ, 454, L149 Rodríguez, L.F., Reipurth, B., 1998, RMxAA, 34, 13

181 BIBLIOGRAPHY 145 Rodríguez, L.F., Reipurth, B., Raga, A.C., Cantó, J. 1998, Rev. Mex. Astron. Astrofis., 34, 69 Rosvick, J.M., Davidge, T.J., 1995 PASP, 107, 49 Sandell, G., Hoglund, B., Kisliakov, A.G., 1983, A&A, 118,306 Sandell, G., Weintraub, D.A., 2001, 134, 115 Saraceno, P., Ceccarelli, C., Clegg, P. et al. 1996, A&A, 315, L293 Sato, F., Fukui, Y. 1989, ApJ, 343, 773 Sato, F., Mizuno, A., Nagahama, T., et al. 1994, ApJ, 435, 279 Serabyn, E., Güsten, R., Mundy, L. 1993, ApJ, 404, 247 Scappini, F., Cecchi-Pestellini, C., Olberg, M., Casolani, A., Fanti, C. 1998, ApJ, 504, 866 Schwartz, P.R., Gee, G., Huang, Y.-L. 1988, ApJ, 327, 350 Schwartz, R.D., Gyulbudaghian, A.L., Wilking, B.A. 1991, ApJ, 370, 263 Smith, H.A., Fischer, J., 1992, ApJ, 398, 99 Smith, H.A., Fischer, J., Mozurkewich, D., Schwartz, P. 1989, Bull. AAS, 20, 1093 Snell, R.L., Edwards, S. 1982, ApJ, 259, 668 Snell, R.L., Bally, J. 1986, ApJ, 303, 683 Snell, R.L., Loren, R.B., Plambeck, R.L. 1980, ApJ, 239, L17 Snell, R.L., Scoville, N.Z., Sanders, D.B., Erickson, N.R. 1984, ApJ, 284, 176 Snell, R.L., Dickman, R.L., Huang, Y.-L. 1990, ApJ, 352, 139 Stapelfeldt, K.R., Scoville, N.Z. 1993, ApJ, 408, 239 Staude, H.J., Neckel, Th. 1991, A&A, 244, L13 Staude, H.J., Neckel, Th. 1992, ApJ, 400, 556 Strom, S.E., Grasdalen, G.L., Strom, K.M. 1974, ApJ, 191, 111

182 146 BIBLIOGRAPHY Strom, K.M., Strom, S.E., Wolff, S.C., Morgan, J., Wenz, M. 1986, ApJS, 62, 39 Strom, K.M., Newton, G., Strom, S.E., et al. 1989a, ApJS, 71, 183 Strom, K.M., Margulis, M., Strom, S.E. 1989b, ApJ, 345, L79 Strom, K.M., Margulis, M., Strom, S.E. 1989c, ApJ, 346, L33 Sugitani, K., Matsuo, H., Nakano, M., Tamura, M., Ogura, K. 2000, AJ, 119, 323 Tafalla, M., Myers, P.C., Wilner, D.J. 1994, in Clouds, Cores and Low Mass Stars, eds. D. Clemens and R. Barvainis, ASP Conference Series, 65, 391 Tafalla, M., Bachiller, R., Wright, M.C.H., Welch, W.J. 1997, 474, 329 Tafalla, M., Myers, P.C., Mardones, D., Bachiller, R., 2000, A&A, 359, 967 Takaba, H., Fukui, Y., Fujimoto, Y. et al. 1986, A&A, 166, 276 Tamura, M., Ohashi, N., Hirano, N., Itoh, Y., Moriarty-Schieven, G.H. 1996, AJ, 112, 2076 Tapia, M., Persi, P., Bohigas, J., Ferrari-Toniolo, M. 1997, AJ, 113, 1769 Tatematsu, K., Umemoto, T., Kameya, O. et al. 1993, ApJ, 404, 643 Terebey, S., Vogel, S.N., Myers, P.C. 1989, ApJ, 340, 472 Tofani, G., Felli, M., Taylor, G.B., Hunter, T.R. 1995, A&AS, 112, 299 Torrelles, J.M., Rodríguez, L.F., Cantó, J., et al. 1983, ApJ, 274, 214 Toth, L.V., Kun, M., 1997 IBVS, 4492, 1 Uchida, Y., Shibata, K. 1985, PASJ, 37, 515 Umemoto, T., Hirano, N., Kameya, O. et al. 1991, ApJ, 377, 510 Ungerechts, H., Walmsley, C.M., Winnewisser, G. 1986, A&A. 157, 207 Verdes-Montenegro, L., Torrelles, J.M., Rodríguez, L.F., et al. 1989, ApJ, 346, 193 Vrba, F.J., Luginbuhl, C.B., Strom, S.E., Strom, K.M., Heyer, M.H. 1986, AJ, 92, 633

183 BIBLIOGRAPHY 147 Wang, Y., Evans II, N.J., Zhou, S., Clemens, D.P. 1995, ApJ, 454,217 Weikard, H., Wouterloot, J.G.A., Castets, A., Winnewisser, G., Sugitani, K. 1996, A&A, 309, 581 Weintraub, D.A. 1990, ApJS, 74, 575 Weintraub, D.A, Kastner, J., 1993, ApJ, 411, 767 Weintraub, D.A., Sandell, G., Duncan, W.D. 1991, ApJ, 382, 270 Werner, M.W., Becklin, E.E., Gatley, I. et al. 1979, MNRAS, 188,463 Wilking, B.A., Mundy, L.G., Blackwell, J.H., Howe, J.E. 1989, ApJ, 345, 257 Wilking, B.A., Blackwell, J.H., Mundy, L.G. 1990, AJ, 100, 758 Wilking, B.A., Mundy, L.G., McMullin, J., Hezel, T., Keene, J. 1993, AJ, 106, 250 Wilking, B.A., Claussen, M.J., Benson, P.J., et al. 1994, ApJ, 431, L119 Whittet, D.C.B., Smith, R.G., Adamson, A.J. et al. 1996, ApJ, 458, 363 Wouterloot, J.G.A., Walmsley, C.M. 1986, A&A, 168, 237 Wouterloot, J.G.A., Brand, J., Fiegle, K. 1993, A&AS, 98, 589 Xiang, D., Turner, B.E. 1995, ApJS, 99, 121 Yang, J., Fukui, Y., Umemoto, T., et al. 1990, ApJ, 362, 538 Yang, J., Umemoto, T., Iwata, T., Fukui, Y. 1991, ApJ, 373, 137 Yang, J., Ohashi, N., Fukui, Y. 1995, ApJ, 455, 175 Yang, J., Ohashi, N., Yan, J. et al. 1997, ApJ, 475, 683 Yao, Y, Ishii, M., Nagata, T., Nakaya, H., Sato, S., 2000, ApJ, 542, 392 Yun, J.L., Clemens, D.P. 1994a, ApJS, 92, 145 Yun, J.L., Clemens, D.P. 1994b, AJ, 108, 612 Yun, J.L., Clemens, D.P. 1995, AJ, 109, 742

184 148 BIBLIOGRAPHY Yun, J.L., Moreira, M.C., Torrelles, J.M., Afonso, J.M., Santos, N.C. 1996, AJ, 111, 841 Zavagno, A., Molinari, S., Tommasi, E., Saraceno, P., Griffin, M. 1997, A&A, 325, 685 Zhou, S., Wu, Y., Evans, N.J., et al. 1989, ApJ, 346, 168 Ziener, R., Eislöffel, J. 1999, A&A, 347, 565 Zinchencko, I., Henning, Th., Schereyer, K. 1997, A&A, 124, 385 Zinnecker, H., Bastien, P., Arcoragi, J.P., Yorke, H.W., 1992, A&A, 265, 726

185 Chapter 3 Infrared images, 1.3 mm continuum and ammonia line observations of IRAS Introduction The IRAS source is the exciting star of the Herbig-Haro object HH 120 (Cohen & Schwartz 1987). It is located inside the cometary globule CG30 which belongs to the Gum Nebula complex. CG30 is also identified with the dark cloud DC (Hartley et al. 1986), and is characterized by the presence of a small ( 15 ) patch of optical nebulosity. Optical polarization measurements obtained by Scarrott et al. (1990) indicate that this is a diffuse reflection nebula containing the Herbig-Haro knot HH 120. IRAS is coincident with the near-ir source CG30-IRS4 found by Pettersson (1984). The very steep spectral index observed in the infrared energy distribution and the derived bolometric luminosity of 16 L (Persi et al. 1990) (D=400 pc) indicate that the source is a very young, low-mass stellar object probably with a collimated outflow as suggested by the detection of H 2 emission at the position of HH 120 (Schwartz et al. 1987). Near-IR images of low-luminosity candidate protostars in Taurus obtained by Tamura et al. (1991), have shown the presence of infrared nebulosities probably 149

186 150 Chapter 3. Observations of IRAS due to scattering of radiation from the central source by the dust associated with the mass outflow extending to the poles of a circumstellar disk. Evidence for such circumstellar disks in young stellar objects have been found using submm and mm continuum observations (Adams et al. 1990; André et al. 1990; Beckwith et al. 1990). In this chapter we present the results of near-ir images, 1.3 mm and 3.6 cm continuum, and ammonia line observations of the IRAS source In Section 3.2 we describe our observations. In Section 3.3 we discuss the morphology of the infrared nebula detected from the images as well as the infrared energy distribution from 1.2 μm to 1.3 mm, and we derive the parameters of a possible circumstellar disk from the detected 1.3 mm flux density. Finally, we derive from the ammonia data the physical parameters of the observed high density core where IRAS is embedded. In Section 3.4 we summarize our conclusions. 3.2 Observations Near-infrared images J, H, K, and L broad-band images of IRAS were obtained during the night of 22 January 1992 using the ESO s Infrared Array Camera (IRAC-1) attached to the ESO/MPI 2.2 m telescope at La Silla (Chile). At the epoch of our observations IRAC-1 was equipped with a Hg:Cd:Te array from Phillips Components Ltd. The images were collected with a scale of 0. 8/pix in beam switching mode, where the telescope alternates automatically between the source (A) and a reference sky position (B), separated by 50 in R.A. Images were acquired in ABBA sequences. This mode as well as the performances and characteristics of the infrared camera are described in the ESO operating Manual (Moneti 1991). A total exposure time of about 18 minutes (half on the source and half on the sky) was used for all the filters. In order to calibrate the images we observed several standard stars (at least four during the night) taken from the list of ESO standard stars. The night was photometric as shown by the small standard deviation of the zero points in the four filters (±0.03 mag). The images were processed (sky subtracted and flat fielded) using the IRAF packages. We determined a point spread function of (FWHM). Figure 3.1 shows the J, H, K, and L surface brightness images of IRAS The total field of view of each frame is

187 3.2. Observations 151 Figure 3.1: J, H, K, and L surface brightness images of IRAS The presence of an infrared nebulosity is evident especially in J and H, while the K and L bands are dominated by the emission from the exciting star coincident with the point-like IRAS source. The contribution of the star has been separated from the nebula by deconvolving the images with the observed point spread function. According to our calibration obtained from the standard stars, we derived the near- IR flux densities of both, the point-like source and of the nebula. The photometry of the illuminating star corresponds to a beam of 4. In Table 3.1 we give the photometry of the star, of the nebula and the integrated photometry of the source. The uncertainties in the brightness are ±0.15 mag. Our integrated photometry derived from the images is comparable to that obtained by Persi et al. (1990) using

188 152 Chapter 3. Observations of IRAS an aperture of 12. As one can see from the observed colours, the illuminating star is redder than its associated nebula. Table 3.1: IR photometry Source J H K L IRAS nebula IRAS+nebula mm continuum emission Observations of 1.3 mm continuum emission of IRAS , were performed using the MPIfR 3 He-cooled bolometer (Kreisa 1990) at the SEST 15 m submillimeter telescope on La Silla (ESO, Chile) during an observing run on The beam size was 30, and the absolute accuracy in deriving the flux density was approximately 15%; further observational details can be found in Reipurth et al. (1993). The observed flux density of IRAS was 602 ± 40 mjy. Reipurth et al. (1993) obtained 1.3 mm continuum observations of the same source using the same instrument but with a beam size of only 23. Their measured flux density of 470 ± 12 mjy indicates that IRAS is extended at mm wavelengths cm continuum emission We made 3.6 cm continuum observations in 1992 July 16 with the Very Large Array of the NRAO 1 in the D configuration. The phase center of the field observed was located at the position of the IRAS source (α(1950) = 08 h 07 m 40 ṣ 2, δ(1950) = ). We used 3C286 for flux calibration, with an adopted 3.6 cm flux of 5.27 Jy. The phase calibrator was with a bootstrapped flux of 1.47±0.03 Jy. The data were edited and calibrated following the standard VLA procedures. Cleaned maps with natural weight were obtained with the task MX of AIPS. We 1 The National Radio Astronomy Observatory is operated by Associated Universities Inc., under cooperative agreement with the National Science Foundation

189 3.2. Observations 153 made a map of pixels with a cellsize of 2 in order to include confusing sources close to the first secondary lobe of the primary beam pattern, and to be able to clean their sidelobes. The resulting synthesized beam size was (p.a.= 12 ) and the rms noise achieved was 52 μjy. We detected a source at α(1950) = 08 h 07 m 20 ṣ 9, δ(1950) = ± 1, with an integrated flux density (corrected for primary beam response) of 6.6 ± 0.3 mjy. Thissourceislocatedfarfromthe center of the field and it is probably an extragalactic background source, since for the sensitivity we achieved the expected number of such background sources within one primary VLA beam is N =3± 2, as can be estimated from an extrapolation to 8.4 GHz of the results of Condon (1984). We do not detect any source towards the cometary globule CG30 above a 5 σ level of 0.26 mjy Ammonia line observations We carried out observations of the (J, K) =(1, 1) and (2, 2) inversion lines of the ammonia molecule with the 37 m radio telescope at Haystack Observatory 2 in January At the frequency of these transitions ( 23.7 GHz) the half power beam width of the telescope is 1. 4 and the beam efficiency at an elevation of 40 is 0.4. We used a cooled K-band maser receiver and the new 5000-channel autocorrelation spectrometer with a full bandwidth of 17.8 MHz. The calibrations were made with the standard noise-tube method. The spectra were corrected for elevation-dependent gain variations and for atmospheric attenuation. The rms pointing error of the telescope was 10. System temperature was 140 K. The observations were made in the position switching mode. We made an NH 3 (1,1) five-point map with full beam separation between points, centered on the position of IRAS We also observed the NH 3 (2,2) transition towards the central position of the map. Data were reduced using the CLASS and GRAPHIC packages of the IRAM. All data are given in a main-beam brightness temperature (T MB ) scale. The observed spectra were smoothed, resulting a velocity resolution of 0.11 km s 1. Typical 1-σ sensitivity achieved in T MB was 0.2 K per spectral channel of 0.11 km s 1. In Fig. 3.2 we show a contour plot of the integrated intensity T MB dv of the NH 3 (1,1) transition. As can be seen in this figure, the NH 3 (1,1) emission is unresolved, peaking towards the position of the IRAS source, where T MB =1.8 K. In Fig. 3.3 we show 2 Radio Astronomy at Haystack Observatory of the Northeast Radio Observatory Corporation is supported by the National Science Foundation.

190 154 Chapter 3. Observations of IRAS Figure 3.2: Contour map of the integrated intensity, T MB dv,ofthenh 3 (1,1) transition. Contour levels are 0.75, 1, 1.25, 1.5, and 1.75 K km s 1. The position of IRAS is indicated with a large cross. The observed positions are indicated with a small cross. The half-power beam of the telescope is also indicated. the observed NH 3 (1,1) spectrum towards this position. We do not detect NH 3 (2,2) emission, obtaining a 3-σ upper limit of 0.6 K.

191 3.3. Discussion 155 Figure 3.3: Spectrum of the (J, K) =(1, 1) inversion line of NH 3 observed towards the position of IRAS Discussion Infrared nebulosity The J, H, and K images of Fig. 3.1 and the relative contour maps of Fig. 3.4 indicate the presence of an infrared nebulosity extending approximately 13 8 corresponding to AU at a distance of 400 pc. While in J and partially in H the emission is dominated by the nebula, the K and specially the L images show clearly the embedded young star which position is coincident with IRAS (position (0, 0) in Fig. 3.4). This is well demostrated by the cross-cut plots along the EW direction shown in Fig Morphologically, the infrared nebula shows a bright knot 4 E of the IRAS source, and a second peak at the position of the Herbig-Haro object HH 120 (crosses in the J, H, K contour maps of Fig. 3.4) observed mainly in the J and H images. According to Graham & Heyer (1989), HH 120 is not easily distinguished in the broad-band IR images because most of the near-ir emission of HH objects is due to the H 2 emission line. The IR nebula is very similar to the optical nebulosity found

192 156 Chapter 3. Observations of IRAS Figure 3.4: Contours maps of IRAS The lowest contour and contour step in 10 7 Jy/pix are as follows: J (1.25,1.62), H (1.60,5.0), K (5.0,12.3), L (170,50). IRAS is located at position (0, 0). The crosses in the J, H and K images indicate the position of HH 120 by Pettersson (1984), and interpreted by Scarrott et al. (1990) as an amorphous reflection nebula containing HH 120. Infrared nebulae appear to be associated with several cold IRAS sources in cloud cores which are believed to be low-mass protostar candidates (Heyer et al. 1990; Tamura et al. 1991). Their nature is explained by scattering of radiation from the central source by the dust associated with mass outflow extending along the axis of a circumstellar disk. This could be the case of the infrared nebula observed in the cometary globule CG30.

193 3.3. Discussion Energy distribution We have obtained the energy distribution of the exciting star IRAS , combining our near-ir photometry of Table 3.1 for a 4 aperture, the IRAS data taken from the point source catalogue (PSC), and the observed 1.3 mm flux density (Fig. 3.6). In addition, we have included the integrated near-ir flux densities obtained with a beam of 12 (Persi et al. 1990), and the submillimiter and millimeter continuum observations of Reipurth et al. (1993). Applying the relationship given by Myers et al. (1987) between the observed near-ir photometry and the visual extinction, we have determined A V =32±6mag. The μm luminosity of 19 L derived for this source integrating the spectrum of Fig. 3.6 is in good agreement with the previous determination of Persi et al. (1990). Only a small fraction ( 3%) of this luminosity is emitted in the near-ir. The observed strong continuum millimeter emission and the shape of the energy distribution suggest, according to Reipurth et al. (1993) and Terebey et al. (1993), the presence of a cold circumstellar disk inclined toward the line of sight, surrounding the HH energy source. A rough valuation of the parameters of such a disk (dust temperature T d and dust mass M d ) can be obtained from the observed flux densities at 100 and 1300 μm. Using Eqs. 1 and 5 of Reipurth et al. (1993), and assuming the absorption coefficient k 1300 =0.003 cm 2 /g (Chini et al. 1987), for an emissivity law of the type ν m with m =1, 2wederiveT d = KandM d =( ) 10 2 M. It is evident from Fig. 3.6 that the IRAS source has a very steep spectrum with the spectral index n = d log λf λ /d log λ =1.4between 2.2 and 25 μm. This indicates that the source is a possible candidate protostar (Class I source in the classification of Lada 1987). Lada (1991) noted that a few Class I sources display extremelly steep infrared energy distributions and proposed that these objects, which he designated Extreme Class I sources, are the youngest among Class I sources. Later, André etal. (1993) noted that these objects are much stronger at mm and submm wavelengths than typical Class I sources, interpreting this result as indicative of much more massive circumstellar structures, independently of geometry. André et al. (1993) suggest that these sources make up a new class of young stellar objects, which they designate as Class 0 sources. These authors propose an age-ordering criterion of embedded objects in terms of the ratio of a source s bolometric luminosity L bol to its 1.3 mm luminosity L 1.3 =4πD 2 S 1.3 Δν (corresponding to an integrated 1.3

194 158 Chapter 3. Observations of IRAS mm flux density S 1.3 and a bandpass Δν = 50 GHz), defining as Class 0 objects those sources which have a ratio L bol /L 1.3 < André et al. (1993) list eight candidate Class 0 sources for which this ratio L bol /L 1.3 = , while for typical Class I sources this ratio is much higher. Unlike the Class 0 candidates proposed by André et al. (1993), IRAS is detected in the near-ir; however, we note that for IRAS we obtain a ratio L bol /L 1.3 =1 10 4, which is similar to those found for the proposed extremely young Class 0 sources, and significantly lower than for typical Class I sources. André et al. (1993) also propose an alternative age-ordering criterion for embedded young stellar objects based on their dust temperature T d, noting that younger objects should be colder. For the candidate Class 0 sources listed by André etal. (1993) T d ranges from 20 to 39 K. We note, again, that IRAS , has a dust temperature T d 20 K similar to the that of the coldest Class 0 sources. We thus propose that IRAS is also a very young source similar, in terms of 1.3 mm luminosity and dust temperature, to the Class 0 sources proposed by André et al. (1993). Eiroa et al. (1994) note that a significant fraction of Class 0 candidates are associated with HH objects (B335: Vrba et al. 1986, Reipurth et al. 1992; L1527, L1448: Eiroa et al. 1994), suggesting that HH emission is a common phenomenon among extremelly young objects. Since our results indicate that IRAS is a very young emmbeded object, its association with HH emission (Pettersson 1984) and shocked H 2 emission (Schwartz et al. 1987) further suggest that the outflow phenomenon starts very early in protostellar evolution. Finally, comparing our observed 1.3 mm flux density with the corresponding measurement obtained with a different beam size by Reipurth et al. (1993) (see Fig. 3.6), we conclude that IRAS is extended also at this wavelength. This result seems to be in agreement with that obtained by André (1991) who found extended 1.3 mm emission of a few candidade protostars in ρ 0ph Dense core Ammonia observations are an excellent probe of the dense cores in dark clouds. In order to obtain the ammonia line parameters for the core associated with IRAS (Fig. 3.2), we fitted with the CLASS program the intensities of the magnetic hyperfine components to the NH 3 spectrum observed towards the position

195 3.3. Discussion 159 Figure 3.5: Cross-cut plot along the E-W direction of the J, H and K images of IRAS

196 160 Chapter 3. Observations of IRAS Table 3.2: Parameters from ammonia observations V LSR (1; 1) a 6:15 ± 0:02 km s 1 V 1=2 (1; 1) b 0:76 ± 0:05 km s 1 fi m (1; 1) c 1:1 ± 0:4 f T ex fi m (1; 1) d 3:1 ± 0:3 K f N(1; 1) e 6: cm 2 f N(2; 2) f < ο 6: cm 2 T rot g < ο 15 K f N(H 2 ) h ο 1: cm 2 A V i Distance j ο 18 mag 400 pc Angular size k < ο Linear size k ο < 0.16 pc Mass l ο 6 Mfi Virial Mass m ο < 10 Mfi n(h 2 ) n > ο cm 3 a Radial velocity ofthe(1; 1) line with respect to the Local Standard of Rest. b Intrinsic linewidth, taking into account the optical depth and the magnetic hyperfine components of the (1; 1), but not the spectral resolution of the spectrometer. c Optical depth of the main line of the (1; 1), calculated as the sum of the optical depths of its magnetic hyperfine components. d Derived from the transfer equation, assuming Tex fl T bg =2:7 K,wheref is the beam filling factor, and T ex is the excitation temperature. e Beam averaged column density in the (1; 1) level, obtained assuming Tex fl T bg (e.g., Takano 1986). f 3-ff upper limit to the beam averaged column density inthe(2; 2) level. g Upper limit to the rotational temperature, calculated from the column density ratio in the (1; 1) and (2; 2) levels. h Beam averaged H2 column density, obtained assuming LTE for the rotational metastable states of NH 3 at the same T rot = T k = 11 K (derived from CO data of Torrelles et al. 1983), and adopting a relative abundance X(NH 3 )=10 8 (Herbst & Klemperer 1973). i Visual extinction, obtained from [AV =mag] = 10 [N (H 2 )=10 22 cm 2 ] (Dickman 1978). j Pettersson 1984 k As the source is unresolved, the upper limit is given by the size of the beam. l Obtained from the beam averaged column density and the size of the beam. Note that although the source is unresolved this estimation is independent of the size of the source. m Obtained from [Mvir =Mfi] = 210[R=pc][ V 1=2=km s 1 ] 2,whereR is the radius of the source. n Lower limit to the H2 volume density, estimated from the two-level model (Ho & Townes 1983), assuming T k =11Kandf =1. This estimation is independent of the NH 3 abundance.

197 3.3. Discussion 161 Figure 3.6: μm energy distribution of IRAS (open square) near-ir photometry with a beam of 4 ; (filled square) near-ir photometry of Persi et al. (1990) beam of 12 ; (filled triangle) IRAS PSC data; (open triangle) 1.3 mm continuum beam of 30 ; (filled circle) submm and mm observations of Reipurth et al. (1993) with a beam of 18 and 23 respectively of the emission peak (Fig. 3.3). In Table 3.2 we give the parameters obtained from this fit. Physical parameters for the high density core are also given in Table 3.2. These parameters have been derived from the NH 3 data following the procedures explained in the footnotes of the table. Among these parameters is the NH 3 rotational temperature, which constitutes a good estimation of the kinetic temperature of the high density clump and for which we found an upper limit, T rot < 15 K in agreement with the kinetic temperature of T k = 11 K that can be derived from the CO data of Torrelles et al. (1983). Adopting an ammonia abundance X(NH 3 )=10 8 (Herbst & Klemperer 1973) we derived a beam averaged H 2 column density of cm 2, implying a visual extinction A V 25 mag, consistent with that derived from IR observations. The high density core appears unresolved by our telescope beam of 1. 4(see Fig. 3.2), implying that its physical size is < 0.16 pc, for an adopted distance of 400 pc. From the beam averaged column density and the beam size, we estimate amassof8m for the high density core, in agreement with the virial mass. This

198 162 Chapter 3. Observations of IRAS suggests that the adopted NH 3 abundance is adequate for the IRAS high density core. This is further supported by the agreement between the H 2 volume density n(h 2 ) 10 4 cm 3, obtained from the two-level model (independent of the NH 3 abundance), and that resulting by dividing the column density and the size of the core. With our angular resolution, the ammonia emission peak coincides with the position of IRAS (Fig. 3.2), suggesting that this source is embedded in the dense core traced by the ammonia emission. Dense cores associated with IRAS sources are common in nearby dark clouds such as those studied by Benson & Myers (1989). 3.4 Conclusions From our observations it results that IRAS is a low-mass protostellar object embedded in a dense core with physical characteristics (temperature, linewidth, mass and size) similar to those of nearby dark clouds detected by Benson & Myers (1989). High spatial resolution near-ir images of this source, exciting the Herbig-Haro object HH 120, show the presence of an infrared nebulosity extending E-W direction approximately 6000 AU. This kind of nebulosity found associated with several canditate low-mass protostars (Tamura et al. 1991) can be indicative of circumstellar dust disk and of mass outflow from the embedded sources. This circumstellar disk surrounding our source should have a dust temperature of 20 K and a dust mass of M as derived from the observed 100 and 1300 μm flux densities. In addition, there is evidence that this cold envelope is also extended. In conclusion, our observations show that IRAS is a young source embedded in a dense core, surrounded by a dense disk and large envelope in agreement with the models of Adams et al. (1987). Our results suggest that IRAS is placed among the youngest Class I sources, with a large 1.3 mm luminosity and low dust temperature, similar to those of the extremely young Class 0 candidates proposed by André et al. (1993). As IRAS is the exciting source of HH 120, our results suggest also that HH outflows start very early in protostellar evolution.

199 Bibliography Adams F.C., Lada C.J., Shu F. 1987, ApJ, 312, 788 Adams F.C., Emerson J.P., Fuller G.A. 1990, ApJ, 357, 606 André, P., Montmerle, T., Feigelson, E.D., Steppe, H. 1990, A&A, 240, 321 André, P. 1991, in Young Star Clusters and Early Stellar Evolution, eds. F. Palla, P. Persi, H. Zinnecher, Mem. Soc. Astron. Ital., 62, 829 André, P., Ward-Thompson, D., Barsony, M. 1993, ApJ, 406, 122 Beckwith, S.V.W., Sargent, A.J., Chini, R.S., Gusten R. 1990, AJ, 99, 924 Benson, P.J., Myers, P.C. 1989, ApJS, 71, 89 Chini, R., Krügel, E., Wargau, W.F. 1987, A&A, 181, 378 Cohen, M., Schwartz, R.D. 1983, ApJ, 265, 877 Condon, J.J. 1984, ApJ, 287, 461 Eiroa, C., Miranda, L.F., Anglada, G., Estalella, R., Torrelles, J.M. 1994, A&A, 283, 973 Graham, J.A., Heyer, M.H. 1989, PASP, 101, 573 Hartley, M., Manchester, R.N., Smith, R.M., Tritton, S.E., Goss, W.M. 1986, A&AS, 63, 27 Herbst, E., Klemperer, W. 1973, ApJ, 185, 505 Heyer, M.H., Ladd, P.C., Myers, P.C., Campbell, B. 1990, AJ, 99, 1585 Ho, P.T.P., Townes, C.H., 1983, ARA&A, 21,

200 164 BIBLIOGRAPHY Kreysa, E. 1990, in From Ground-Based to Space borne Astronomy, Proc. of the 29th Liege Symp., ESA Publications Lada, C.J. 1987, in Star Forming Regions, IAU Symp. No. 115, eds. M. Peimbert, J. Jugaku,(Reidel,Dordrecht), p. 1 Lada, C.J. 1991, in The Physics of Star Formation and Early Stellar Evolution, eds. C.J. Lada & N.D. Kylafis (Dordrecht: Kluwer), p. 329 Moneti, A. 1991, ESO Operating Manual N.15, ESO publications Myers, P.C., Fuller, G.A., Mathieu, R.D. et al. 1987, ApJ, 319, 340 Persi, P., Ferrari-Toniolo, M., Busso, M. et al. 1990, AJ, 99, 303 Pettersson, B. 1984, A&A 139, 135 Reipurth, B. 1983, A&A, 117, 183 Reipurth, B., Chini, R., Krügel, E., Kreysa, E., Sievers, A. 1993, A&A, 273, 221 Reipurth, B., Heathcote, S., Vrba, F. 1992, A&A, 256, 225 Scarrott, S.M., Gledhill, T.M., Rolph, C.H., Wolstencroft, R.D. 1990, MNRAS, 242, 419 Schwartz, R.D., Cohen, M., Williams, P.M. 1987, ApJ, 322, 403 takano, T., 1986, ApJ, 303, 349 Tamura, M., Gatley, I., Waller, W., Werner, M.W 1991, ApJ, 374, L25 Terebey, S., Chandler, C.J., André, P. 1993, ApJ, 414, 759 Torrelles, J.M., Rodríguez, L.F., Cantó, J., Marcaide, J., Gyulbudaghian, A.L. 1983, Rev. Mex. Astr. Astrofis., 8, 147 Vrba, F.J., Luginbuhl, C.B., Strom, S.E., Strom, K.M., Heyer, M.H. 1986, AJ, 92, 633

201 Chapter 4 High angular resolution VLA ammonia study of L Introduction The molecular cloud L1287, located at a distance of 850 pc (see discussion in Yang et al. 1991), contains an energetic bipolar molecular outflow (Snell at al. 1990; Yang et al. 1991). The axis of the outflow is oriented at a P.A.=45 (see Fig. 4.1). The center of the outflow is associated with dense gas, that has been mapped in HCN, HCO + (Yang et al. 1991), NH 3 (Estalella et al. 1993; see also in Chapter 2 of this work), and CS (Yang et al. 1995; McMuldroch et al. 1995). At the center of the outflow there is also a very cold, luminous (L bol = 1800 L ;Mookerjaetal. 1999) IRAS point source, IRAS , that has been proposed as the outflow exciting source. The brightest visible object in the region, RNO 1 (Cohen 1980), lies 40 northeast of the nominal IRAS position. A binary FU Ori system (RNO 1B/1C, whose components are separated by 6 ) was discovered a few arseconds southwest of the nominal IRAS position, inside its error ellipsoid (Staude & Neckel 1991; Kenyon et al. 1993). The nearinfrared imaging of Kenyon et al. (1993) reveal extended emission from RNO 1B/1C along the axis of the molecular outflow, which was interpreted by these authors as scattered light from the cavity created by the outflow. Based on the positional agreement between the RNO 1B/1C pair, the center of the outflow and the IRAS error ellipsoid, and due to the presence of this extended IR emission, Kenyon et al. 165

202 166 Chapter 4. VLA study of ammonia in L1287 Figure 4.1: CO outflow (Yang et al. 1991) and ammonia core (emission above the half-power level; Estalella et al. 1993) in L1287. (1993) proposed that one or perhaps both of these FU Ori stars are the driving source of the outflow. This result lead Kenyon et al. (1993) to propose, in a more general context, that the FU Or eruptions can provide enough energy and momentum to power the molecular outflows observed in star-forming regions. In this sense, L1287 was the best example of association between FU Ori stars and molecular outflows. However, the association of RNO 1B/1C with the L1287 outflow was questioned by Weintraub & Kastner (1993) who, from infrared polarimetric studies of the region, proposed that a previously unidentified YSO, one more deeply embedded than either RNO 1B or RNO 1C, located at the center of symmetry of the polarization pattern is probably the exciting source of the L1287 outflow. The position of this proposed embedded source is displaced 4 to the northeast of RNO 1C and 10 to the northeast of RNO 1B and falls within 1. 5 of the catalog position of IRAS Anglada et al. (1994) detected a 3.6 cm continuum source (VLA 3) at the position predicted by Weintraub & Kastner (1993). Additionally, the VLA 3 source exhibits evidence of elongation along the outflow axis. Sensitive VLA obser-

203 4.1. Introduction 167 vations have revealed that, in general, the driving sources of molecular outflows are associated with cm continuum emission and are elongated along the outflow axes (e.g., Anglada 1995 and references therein). Based on this result, Anglada et al. (1994) suggested that the VLA 3 source is a radio jet, tracing the origin of the outflow, and proposed VLA 3 it as the best candidate for the excitation of the L1287 molecular outflow. Three additional VLA sources were detected near the center of the outflow by Anglada et al. (1994). One of the sources (VLA 1) falls within 2 of the position of RNO 1C, while source VLA 4 falls at 3 of the secondary polarimetric centroid proposed by Wientraub & Kastner (1993). Fiebig (1995) detected H 2 O maser emission associated with VLA 3. Further observations (Fiebig et al. 1996) carried out with higher angular resolution (0. 1) resolved the emission as originating in several maser spots distributed in an elongated structure around VLA 3 of 70 AU in diameter, oriented perpendicularly to the outflow axis. The position-velocity diagram shows a pattern suggestive of a rotating protostellar disk. Fiebig (1997) presents a more detailed modelling in terms of a clumpy structure of infalling material that impacts on the accretion disk. All these maser results give support to the identification of VLA 3 as the origin of the outflow activity. Our single-dish ammonia observations carried out with the Haystack 37-m radio telescope, with an angular resolution of 1. 4(see in Chapter 2), and those of Estalella et al. (1993), with the 100-m Effelsberg radio telescope, with an angular resolution of 40, reveal that the central high-density core is clearly elongated in the northwest-southeast direction, perpendicularly to the axis of the CO outflow (see Figs and 4.1). The deconvolved size of the ammonia core, as obtained from the 100-m map, is pc( pc, from the 37-m data). The ammonia emission peaks very close to the position of IRAS , although the angular resolution of the single-dish observations does not allow to distinguish between the positions of VLA 3, RNO 1B/1C, or the other sources in terms of proximity to the ammonia peak. These observations revealed also a clear velocity gradient along the major axis of the condensation, that was interpreted as due to a rotating core. Towards the ammonia peak, the line width is larger than the average, and a relatively high value of the kinetic temperature of 20 K (higher than the average), indicating the presence of a local heating agent, was inferred

204 168 Chapter 4. VLA study of ammonia in L1287 from these observations. Both, the local heating and the line broadening imply a physical association of the high-density gas with one or more sources. However, the angular resolution of the single-dish ammonia observations is insufficient to disentangle the small-scale structure of the high-density core, in order to separate the relative contribution of each individual object. McMuldroch et al. (1995) present CO and CS maps of the central part of the core, obtained with the OVRO interferometer with angular resolutions of 3-8. These authors favor RNO 1C as the driving source of the molecular outflow because the position of this source appears projected closer to the peak of the mm continuum emission. The CS emission is proposed to be tracing the cavity walls that have been compressed by the outflow wind originated in the FU Ori star RNO 1C. However, Yang et al. (1995) from NMA interferometric CS observations (angular resolution 7 ) found that RNO 1C is located at the intersection between the red and blue CS outflow lobes, but since RNO 1B and VLA 3 also lie on the symmetry axis of the outflow, they favored VLA 3 as the exciting source, because it is more deeply embedded. Recently, Sandell & Weintraub (2001) observed the submillimeter emission with the JCMT telescope. These authors find that the dust emission is more closely associated with RNO 1C, but with an extension of emission towards VLA 3, and probable contributions from other objects such as RNO 1 or VLA 2 and 4, since the angular resolution of their observations (8-14 ) did not allow them to determine which part of the dust emission is associated with each single object. High-angular resolution ammonia observations are most useful to stablish the true association of a given object with molecular gas, through the study of local kinematics, column density and heating. Since the molecular outflow exciting sources should necessarily be associated with surrounding molecular gas, in this chapter, we present sensitive VLA NH 3 observations of the L1287 core with an angular resolution of 4, that will help to clarify the role of the different YSOs in the excitation of the bipolar outflow.

205 4.2. Observations Observations Simultaneous observations of the (J, K) =(1, 1) and (J, K) =(2, 2) inversion transitions of the ammonia molecule (at the rest frequencies and GHz, respectively) were carried out with the VLA of the NRAO 1 in the D configuration in 1996 August 31. The phase center of the interferometer was set at the position of the catalog position of IRAS , α(1950) = 0 h 33 m 53 ṣ 3and δ(1950) = The absolute flux calibrator was 3C48 ( ) for which a flux density of 1.1 Jy at the observed frequency of 24 GHz was adopted. The phase calibrator was , with a boostraped flux density of 1.82 Jy, and was used as bandpass calibrator. The NH 3 (1,1) and NH 3 (2,2) lines were observed simultaneously using the four- IF spectral mode of the VLA, which allows the observation of two polarizations for each line. A bandwidth of MHz was used, with 63 channels of khz width (0.617 km s 1 at λ =1.3 cm) centered at V LSR = 18.0 kms 1, resulting a velocity resolution of 1.2 km s 1 after Hanning smoothing. Calibration and data reduction were performed using standard procedures of the Astronomical Imaging Processing System (AIPS) of the NRAO. Cleaned maps were obtained with the task IMAGR of AIPS. The resulting synthetized beam size, after natural weighting of the visibility data, is (P.A. = 0.5 )andtheachieved1σ noise level per spectral channel is 3 mjy beam Results Cloud structure We detected the NH 3 (1,1) and the NH 3 (2,2) main line emission with the VLA in the velocity range from 20 to 15 km s 1. The inner satellite hyperfine components of the NH 3 (1,1) line are also clearly detected in the same velocity range (outer satellites fall outside our bandwidth). Maps of the individual velocity channels with significant emission are shown in Figs. 4.2, 4.3, and 4.4, for the (1,1) main line, inner 1 The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by the Associated Universities, Inc

206 170 Chapter 4. VLA study of ammonia in L1287 satellite, and (2,2) respectively. The channel maps reveal a clumpy distribution of the ammonia emission with a complex kinematics, with large changes in the spatial distribution of gas from one velocity channel to another. Two main structures are distinguished: a main central core, apparently associated with the FU Ori system RNO1B/C and the sources VLA 1-4, that accounts for most of the observed ammonia emission; and a second core, 40 to the NE of the phase center, apparently associated with the bright, optically visible RNO 1 object. The maps of the zero-order moment (integrated intensity) of the NH 3 (1,1) and the NH 3 (2,2) lines are shown in Figs. 4.5 and 4.6, respectively. These maps show an structure clearly elongated in the northwest-southeast direction, with a position angle of 121, roughly perpendicular to the axis of the CO outflow. This distribution of gas is in good agreement with the results of previous single-dish ammonia observations (Estalella et al. 1993, see Fig. 4.1; see also Fig in of this work). In our VLA maps, the NH 3 (1,1) emission extends 1. 4, corresponding to a projected length of 0.35 pc, assuming a distance of 850 pc (Yang et al. 1991). The core associated with RNO 1 appears, clearly separated, to the north-east of the image (note that the maps presented in the figures have not been corrected for the primary beam response, so the emission near RNO 1 appears significantly weaker that its true value). Spectra of the overall emission of the main core, as well as of the RNO 1 core are shown in Fig The velocity integrated total flux density, as well as other physical parameters of each core, are listed in Table 4.1. The velocity integrated total flux density of the NH 3 (1,1) main line observed with the VLA is 8Jykms 1, which corresponds to 13-23% of that detected in the single-dish observations, as estimated from the Effelsberg and Haystack data (35-60 Jy km s 1 ; Estalella et al. 1993, this work). If the missing flux corresponds to extended emission and was uniformly distributed over an area equal to that observed in the single-dish observations, the resulting intensity would be 7mJybeam 1, and would appear only at the 2σ level in our maps. The integrated intensity maps of both the NH 3 (1,1) and (2,2) lines show three main emission peaks near the center of the main core (see Figs. 4.5 and 4.6). One is located in between the positions of RNO 1B and 1C (Peak 1); another (the most intense; Peak 2) is located somewhat to the NW (within 4 ) of the position of

207 4.3. Results NH 3 (1,1;m) RNO km/s km/s VLA 3 RNO 1C VLA 1 4 RNO 1B VLA km/s km/s km/s km/s DECLINATION (B1950) km/s km/s RIGHT ASCENSION (B1950) Figure 4.2: Countour maps of the velocity channels with significant NH 3 (1,1) main line emission. The LSR velocity of each channel is indicated. Contour levels are 4, 3, 3, 4, 6, 8, 10, 12, 15, 20 and 25 times 3.0 mjy beam 1. The synthetized beam ( , P.A. = 0.5 ) is shown in the bottom righ-hand corner of the top left-hand panel. The grey scale depicts the same emission for clarification. Maps are not corrected for the primary beam response.

208 172 Chapter 4. VLA study of ammonia in L NH 3 (1,1;is) RNO km/s km/s VLA 3 VLA 4 RNO 1C VLA 1 RNO 1B VLA km/s km/s km/s km/s DECLINATION (B1950) km/s km/s RIGHT ASCENSION (B1950) Figure 4.3: Same as Fig. 4.2, but for the NH 3 (1,1) inner satellite line emission.

209 4.3. Results 173 DECLINATION (B1950) KM/S KM/S KM/S KM/S KM/S KM/S RIGHT ASCENSION (B1950) Figure 4.4: Same as Fig. 4.2, but for the NH 3 (2,2) main line emission.

210 174 Chapter 4. VLA study of ammonia in L1287 NH (1,1;m) RNO DECLINATION (B1950) C B AU RIGHT ASCENSION (B1950) NH (1,1;is) RNO DECLINATION (B1950) C B AU RIGHT ASCENSION (B1950) Figure 4.5: Zero-order moment (integrated intensity) of the NH 3 (1,1) main line and the NH 3 (1,1) inner satellite line emission. Countour levels are 3, 6, 9, 12, 15, 20, 25, 30, 35, 40and45times3mJybeam 1 km s 1. The greyscale image depicts the same emission for clarification.

211 4.3. Results 175 NH (2,2;m) RNO DECLINATION (B1950) C B AU RIGHT ASCENSION (B1950) Figure 4.6: Same as Fig. 4.5, but for the NH 3 (2,2) main line emission. the source VLA 3; finally, a third emission peak (Peak 3), is located 8 SE of VLA 4. There is no known stellar object towards Peak 3; however, we note that this emission peak is very close to the position of the secondary polarimetric centroid, that was suggested by Wientraub & Kastner (1993) as the position of an embedded protostar. Figure 4.8 shows the observed spectra towards the three emission peaks, as well as towards the positions of the know stellar objects in the region. Table 4.2 lists line and physical parameters towards these positions. The integrated intensity maps of the NH 3 (1,1) line (main and satellite) show a narrow valley of reduced intensity that crosses the center of the structure at a P.A. of 34 (see Fig. 4.5), similar to that of the CO outflow (P.A. 45 ). Such a decrease in the intensity of the ammonia emission is suggestive of a cavity excavated by the outflow in the molecular core. The presence of such a cavity in the L1287 core was proposed by Kenyon et al. (1993) from near-ir data, and by Yang et al. (1995) and McMuldroch et al. (1995) from CS data. The radio continuum sources VLA

212 176 Chapter 4. VLA study of ammonia in L NH (1,1) 3 Main Core 200 RNO1 Core FLUX DENSITY (Jy) NH (2,2) FLUX DENSITY (Jy) V (km/s) LSR V (km/s) LSR Figure 4.7: Spectra of the NH 3 (1,1) (top) and NH 3 (2,2) (bottom) inversion transitions corresponding to the overall emission of the Main Core (left) and the RNO 1 Core (right). 4 and VLA 2 (Anglada et al. 1994), lie at the center of this local minimum. The decrease in the line intensity is less abrupted in the NH 3 (2,2) integrated intensity map (Fig. 4.6), indicating that towards these positions the column density is lower and the kinetic temperature is higher than in the surrounding, as can be seen in Table 4.2. Despite the clumpyness of the emission, the presence of this cavity at the center of the ammonia structure is easily recognizable in the channel maps. Particularly in the 17.4 and 16.8 kms 1 velocity channel maps (see Fig. 4.2), where it is evident that sources VLA 2 and VLA 4 appear located at the inner walls of this cavity. Sources RNO 1B and RNO 1C (and VLA 1, whose position nearly coincides with RNO 1 C) also appear at the inner the edge of the emission in the 17.4 km s 1 velocity channel. VLA 3 is the only source that appears to be associated

213 4.3. Results NH (1,1) 3 Peak 1 40 Peak 2 35 Peak INTENSITY (mjy/beam) NH (2,2) INTENSITY (mjy/beam) NH (1,1) 3 RNO 1 50 RNO 1B 50 RNO 1C INTENSITY (mjy/beam) NH (2,2) INTENSITY (mjy/beam) V LSR (km/s) V LSR (km/s) V LSR (km/s) Figure 4.8: Spectra of the NH 3 (1,1) and NH 3 (2,2) inversion transitions averaged over aboxof 4 4 centered towards the position of the three emission peaks and the known stellar objects in the region (Table 4.2).

214 178 Chapter 4. VLA study of ammonia in L NH (1,1) 3 VLA 2 30 VLA 3 16 VLA INTENSITY (mjy/beam) NH (2,2) INTENSITY (mjy/beam) V LSR (km/s) V LSR (km/s) V LSR (km/s) Figure 4.8: Continued with ammonia emission over almost all the velocity range Velocity distribution The first-order moment (intensity weighted mean V LSR )mapsofthenh 3 (1,1) main line and inner satellite emission are shown in Figs. 4.9 and As can be seen in the figure, there is a clear velocity gradient, with the velocity increasing from NW to SE, along the major axis of the main core. This result is in agreement with the previous single-dish results (Estalella et al. 1993; of this work), that showed a velocity gradient that was interpreted as overall rotation of the core. In Fig we show a velocity-position cut along the major axis of the cloud that further illustrates this result. From this velocity-position cut (from the weak emission extending up to large distances of the center), it can be derived the systemic velocity of the cloud, 17.6 kms 1, in agreement with the results of other authors (e.g., Yang et al obtain a velocity of 18 km s 1 ).

215 4.3. Results RNO 1 NH (1,1;m) DECLINATION (B1950) C B AU RIGHT ASCENSION (B1950) Figure 4.9: Map of the first-order moment (intensity weighted mean V LSR ) of the NH 3 (1,1) main line, superposed on the contour map of the (1,1) integrated intensity (zero-order moment). The V LSR scale ranges from 15.5 to 19.1 km s 1. However, the kinematics is complex, with velocity changes associated with the clumpy substructure. For example, the velocity increases along the minor axis of the structure when moving from Peak 1 to Peak 2, as can be seen in the maps of the first-order moment (Figs. 4.9 and 4.10), as well as in the corresponding velocityposition cut shown in Fig The kinematics in the close environment of VLA 3 is still more complicated. It is interesting to note that in the channel maps (Figs 4.2, 4.3 and 4.4) the ammonia emission appears more extended in the channels of low relative velocity, while it appears more compact in the high velocity (relative to the systemic or central velocity) channels. If the overall velocity gradient along the major axis of

Dense gas and the nature of the outflows,

Dense gas and the nature of the outflows, Astronomy & Astrophysics manuscript no. densegas-rev3 c ESO 2010 October 25, 2010 Dense gas and the nature of the outflows, I. Sepúlveda 1, G. Anglada 2, R. Estalella 1, R. López 1, J.M. Girart 3, and

More information

Emission of High-Density Tracer Molecules in Star Forming Regions

Emission of High-Density Tracer Molecules in Star Forming Regions Universitat de Barcelona Departament d Astronomia i Meteorologia Emission of High-Density Tracer Molecules in Star Forming Regions Òscar Morata Chirivella UNIVERSITAT DE BARCELONA Departament d Astronomia

More information

Near-Infrared Imaging Observations of the Orion A-W Star Forming Region

Near-Infrared Imaging Observations of the Orion A-W Star Forming Region Chin. J. Astron. Astrophys. Vol. 2 (2002), No. 3, 260 265 ( http: /www.chjaa.org or http: /chjaa.bao.ac.cn ) Chinese Journal of Astronomy and Astrophysics Near-Infrared Imaging Observations of the Orion

More information

The origin of the HH 7 11 outflow

The origin of the HH 7 11 outflow 06 (08.06.2 09.09.1 09.10.1 09.13.2 13.18.8) The origin of the HH 7 11 outflow R. Bachiller 1,F.Gueth 2, S. Guilloteau 3,M.Tafalla 1, and A. Dutrey 3 1 IGN Observatorio Astronómico Nacional, Apartado 1143,

More information

The cross-correlation among tracers of the underlying large-scale mass distribution in the universe

The cross-correlation among tracers of the underlying large-scale mass distribution in the universe The cross-correlation among tracers of the underlying large-scale mass distribution in the universe Ignasi Pérez i Ràfols Aquesta tesi doctoral està subjecta a la llicència Reconeixement- NoComercial CompartirIgual

More information

The study of the high-density gas distribution in SFRs with the SRT: the test cases of L1641-S3 and CepA-East

The study of the high-density gas distribution in SFRs with the SRT: the test cases of L1641-S3 and CepA-East Mem. S.A.It. Suppl. Vol. 10, 159 c SAIt 2006 Memorie della Supplementi The study of the high-density gas distribution in SFRs with the SRT: the test cases of L1641-S3 and CepA-East C. Codella 1, M.T. Beltrán

More information

arxiv:astro-ph/ Jan 2000

arxiv:astro-ph/ Jan 2000 Mon. Not. R. Astron. Soc. 000, 000 000 (0000) Printed 30 January 2002 (MN LATEX style file v1.4) Ammonia observations of the nearby molecular cloud MBM 12 José F.Gómez, 1 Joaqu n Trapero, 1;2 Sergio Pascual,

More information

VLA and BIMA observations toward the exciting source of the massive HH outflow

VLA and BIMA observations toward the exciting source of the massive HH outflow VLA and BIMA observations toward the exciting source of the massive HH 80-81 outflow Y. Gómez, L.F. Rodríguez Centro de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari) 58089 Morelia, Michoacán,

More information

arxiv:astro-ph/ v1 29 Oct 2004

arxiv:astro-ph/ v1 29 Oct 2004 arxiv:astro-ph/0410727v1 29 Oct 2004 a II indecates HII region; H indicates optical jet or HH object; 2 indicates H 2 jet; W indicates water maser; I indicates infall or collapse. b The maps of these sources

More information

U UNIVERSITAT DE BARCELONA B. Exploring the Evolution of Dark Energy and its Equation of State UNIVERSITAT DE BARCELONA

U UNIVERSITAT DE BARCELONA B. Exploring the Evolution of Dark Energy and its Equation of State UNIVERSITAT DE BARCELONA UNIVERSITAT DE BARCELONA Departament d Astronomia i Meteorologia Exploring the Evolution of Dark Energy and its Equation of State U UNIVERSITAT DE BARCELONA B Memòria presentada per Cristina España i Bonet

More information

American Standard Code for Information Interchange. Atmospheric Trace MOlecule Spectroscopy. Commission Internationale de l Eclairage

American Standard Code for Information Interchange. Atmospheric Trace MOlecule Spectroscopy. Commission Internationale de l Eclairage Apèndix A Llista d acrònims AEDOS AOT ASCII ATMOS CIE CLAES CMF CFC COST DISORT DOAS DWD ECMWF ERS Advanced Earth Observing Satellite Aerosol Optical Thickness American Standard Code for Information Interchange

More information

CO J = 2 1 MAPS OF BIPOLAR OUTFLOWS IN MASSIVE STAR-FORMING REGIONS

CO J = 2 1 MAPS OF BIPOLAR OUTFLOWS IN MASSIVE STAR-FORMING REGIONS The Astronomical Journal, 129:330 347, 2005 January # 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A. CO J = 2 1 MAPS OF BIPOLAR OUTFLOWS IN MASSIVE STAR-FORMING REGIONS

More information

Two new T Tauri stars and a candidate FU Orionis star associated with Bok globules

Two new T Tauri stars and a candidate FU Orionis star associated with Bok globules Astron. Astrophys. 320, 167 171 (1997) ASTRONOMY AND ASTROPHYSICS Two new T Tauri stars and a candidate FU Orionis star associated with Bok globules J.L. Yun 1, M.C. Moreira 1, J.F. Alves 1, and J. Storm

More information

HIGH RESOLUTION H 2 OBSERVATIONS OF HERBIG-HARO FLOWS

HIGH RESOLUTION H 2 OBSERVATIONS OF HERBIG-HARO FLOWS RevMexAA (Serie de Conferencias), 13, 16 20 (2002) HIGH RESOLUTION H 2 OBSERVATIONS OF HERBIG-HARO FLOWS Antonio Chrysostomou, 1 Chris Davis, 2 and Michael Smith 3 RESUMEN Presentamos observaciones terrestres

More information

Self-consistent Green's functions with three-body forces

Self-consistent Green's functions with three-body forces Self-consistent Green's functions with three-body forces Arianna Carbone Aquesta tesi doctoral està subjecta a la llicència Reconeixement 3.0. Espanya de Creative Commons. Esta tesis doctoral está sujeta

More information

L ORIGEN DE LA VIDA THE ORIGIN OF LIFE

L ORIGEN DE LA VIDA THE ORIGIN OF LIFE L ORIGEN DE LA VIDA Xavier Hernández Alias 1 1 Estudiant de Bioquímica, Universitat de Barcelona xa.he.al@gmail.com Resum Alexander Oparin estableix en el seu llibre L'origen de la vida la base d'una nova

More information

between the H and CO emission and velocity spurs in the PV diagram. It is our best example of the

between the H and CO emission and velocity spurs in the PV diagram. It is our best example of the THE ASTROPHYSICAL JOURNAL, 54:95È945, 000 October 0 ( 000. The American Astronomical Society. All rights reserved. Printed in U.S.A. CO OUTFLOWS FROM YOUNG STARS: CONFRONTING THE JET AND WIND MODELS CHIN-FEI

More information

Mm/Submm images of Herbig Haro energy sources and candidate protostars

Mm/Submm images of Herbig Haro energy sources and candidate protostars A&A 369, 155 169 (2001) DOI: 10.1051/0004-6361:20010097 c ESO 2001 Astronomy & Astrophysics Mm/Submm images of Herbig Haro energy sources and candidate protostars R. Chini 1, D. Ward-Thompson 2,J.M.Kirk

More information

New observational techniques and analysis tools for wide field CCD surveys and high resolution astrometry

New observational techniques and analysis tools for wide field CCD surveys and high resolution astrometry UNIVERSITAT DE BARCELONA Departament d Astronomia i Meteorologia New observational techniques and analysis tools for wide field CCD surveys and high resolution astrometry Memòria presentada per Octavi

More information

Revista Mexicana de Astronomía y Astrofísica ISSN: Instituto de Astronomía México

Revista Mexicana de Astronomía y Astrofísica ISSN: Instituto de Astronomía México Revista Mexicana de Astronomía y Astrofísica ISSN: 0185-1101 rmaa@astroscu.unam.mx Instituto de Astronomía México Anglada, G.; Rodríguez, Luis F. VLA Detection of the Exciting Sources of the Molecular

More information

WHICH ARE THE YOUNGEST PROTOSTARS? DETERMINING PROPERTIES OF CONFIRMED AND CANDIDATE CLASS 0 SOURCES BY BROADBAND PHOTOMETRY

WHICH ARE THE YOUNGEST PROTOSTARS? DETERMINING PROPERTIES OF CONFIRMED AND CANDIDATE CLASS 0 SOURCES BY BROADBAND PHOTOMETRY The Astrophysical Journal Supplement Series, 156:169 177, 2005 February # 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A. A WHICH ARE THE YOUNGEST PROTOSTARS? DETERMINING

More information

Phase-field study of transient stages and fluctuations in solidification

Phase-field study of transient stages and fluctuations in solidification Phase-field study of transient stages and fluctuations in solidification Raúl Benítez Iglesias Departament de Física Aplicada Universitat Politècnica de Catalunya A mi padre, y a su nieta Clàudia. Phase-field

More information

Treball Final de Grau ANSYS Fluent simulation of a solar chimney Simulació d una xemeneia solar en ANSYS Fluent

Treball Final de Grau ANSYS Fluent simulation of a solar chimney Simulació d una xemeneia solar en ANSYS Fluent Tutors Dra. Alexandra E. Bonet Ruiz Dr. Ricardo Torres Castillo Secció Departamental d Enginyeria Química Treball Final de Grau ANSYS Fluent simulation of a solar chimney Simulació d una xemeneia solar

More information

Millimetre dust emission from northern Bok globules

Millimetre dust emission from northern Bok globules Astron. Astrophys. 326, 329 346 (1997) ASTRONOMY AND ASTROPHYSICS Millimetre dust emission from northern Bok globules R. Launhardt and Th. Henning Astrophysical Institute and University Observatory Jena,

More information

DOCUMENTS DE TREBALL DE LA FACULTAT D ECONOMIA I EMPRESA. Col.lecció d Economia

DOCUMENTS DE TREBALL DE LA FACULTAT D ECONOMIA I EMPRESA. Col.lecció d Economia DOCUMENTS DE TREBALL DE LA FACULTAT D ECONOMIA I EMPRESA Col.lecció d Economia E11/262 The proportional distribution in a cooperative model with external opportunities Camilla Di Luca Università degli

More information

arxiv: v1 [astro-ph] 8 Sep 2008

arxiv: v1 [astro-ph] 8 Sep 2008 Handbook of Star Forming Regions Vol. I Astronomical Society of the Pacific, 2008 Bo Reipurth, ed. The Monoceros R2 Molecular Cloud arxiv:0809.1396v1 [astro-ph] 8 Sep 2008 John M. Carpenter California

More information

Herbig-Haro Objects in the p Ophiuchi Cloud

Herbig-Haro Objects in the p Ophiuchi Cloud Publications of the Astronomical Society of the Pacific 109: 549-553, 1997 May Herbig-Haro Objects in the p Ophiuchi Cloud Bruce A. Wilking, richard D. Schwartz, and Tina M. Fanetti Department of Physics

More information

Soil Mechanics 2015/2016

Soil Mechanics 2015/2016 Soil Mechanics 015/016 EXERCISES - CHAPTER 6 6.1 The purpose of this exercise is to study in a simplified form the movements of the Tower of Pisa (Italy) foundation due to the compressibility of the clay

More information

arxiv: v1 [astro-ph] 15 Nov 2008

arxiv: v1 [astro-ph] 15 Nov 2008 arxiv:0811.2495v1 [astro-ph] 15 Nov 2008 Synergy of multifrequency studies from observations of NGC6334I Andreas Seifahrt 1, Sven Thorwirth 2, Henrik Beuther 3, Silvia Leurini 4, Crystal L Brogan 5, Todd

More information

A STUDY OF THE VARIABILITY OF WATER MASER EMISSION IN A SAMPLE OF YOUNG STELLAR OBJECTS

A STUDY OF THE VARIABILITY OF WATER MASER EMISSION IN A SAMPLE OF YOUNG STELLAR OBJECTS Revista Mexicana de Astronomía y Astrofísica, 39, 311 330 (2003) A STUDY OF THE VARIABILITY OF WATER MASER EMISSION IN A SAMPLE OF YOUNG STELLAR OBJECTS M. A. Trinidad, 1 V. Rojas, 1 J. C. Plascencia,

More information

PMS OBJECTS IN THE STAR FORMATION REGION Cep OB3. II. YOUNG STELLAR OBJECTS IN THE Ha NEBULA Cep B

PMS OBJECTS IN THE STAR FORMATION REGION Cep OB3. II. YOUNG STELLAR OBJECTS IN THE Ha NEBULA Cep B Astrophysics, Vol. 56, No. 2, June, 2013 PMS OBJECTS IN THE STAR FORMATION REGION Cep OB3. II. YOUNG STELLAR OBJECTS IN THE Ha NEBULA Cep B E. H. Nikoghosyan Models for the spectral energy distributions

More information

VLA OBSERVATIONS OF Z CMA: THE ORIENTATION AND ORIGIN OF THE THERMAL JET

VLA OBSERVATIONS OF Z CMA: THE ORIENTATION AND ORIGIN OF THE THERMAL JET Revista Mexicana de Astronomía y Astrofísica, 37, 261 267 (2001) VLA OBSERVATIONS OF Z CMA: THE ORIENTATION AND ORIGIN OF THE THERMAL JET Pablo F. Velázquez 1,2 Instituto de Astronomía Universidad Nacional

More information

The Protostellar Luminosity Function

The Protostellar Luminosity Function Design Reference Mission Case Study Stratospheric Observatory for Infrared Astronomy Science Steering Committee Program contacts: Lynne Hillenbrand, Tom Greene, Paul Harvey Scientific category: STAR FORMATION

More information

BV RI photometric sequences for nine selected dark globules

BV RI photometric sequences for nine selected dark globules ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES Astron. Astrophys. Suppl. Ser. 126, 73-80 (1997) NOVEMBER II 1997, PAGE73 BV RI photometric sequences for nine selected dark globules J.F. Lahulla 1, A. Aguirre

More information

Lecture 26 Low-Mass Young Stellar Objects

Lecture 26 Low-Mass Young Stellar Objects Lecture 26 Low-Mass Young Stellar Objects 1. Nearby Star Formation 2. General Properties of Young Stars 3. T Tauri Stars 4. Herbig Ae/Be Stars References Adams, Lizano & Shu ARAA 25 231987 Lada OSPS 1999

More information

arxiv: v1 [astro-ph.sr] 30 Mar 2011

arxiv: v1 [astro-ph.sr] 30 Mar 2011 Accepted for publication, ApJ, on March 2011 The precession of the HH 111 flow in the infrared arxiv:1103.5919v1 [astro-ph.sr] 30 Mar 2011 Noriega-Crespo, A. 1, Raga, A. C. 2, Lora, V. 3, Stapelfeldt,

More information

Survival analysis issues with interval censored data

Survival analysis issues with interval censored data Survival analysis issues with interval censored data Ramon Oller Piqué PhD Thesis directed by Guadalupe Gómez Melis Universitat Politècnica de Catalunya Vic, maig del 2006 A l Alícia, en Martí, en Joan

More information

A parsec-scale flow associated with the IRAS radio jet

A parsec-scale flow associated with the IRAS radio jet submitted to The Astrophysical Journal Letters A parsec-scale flow associated with the IRAS 16547 4247 radio jet Kate J. Brooks Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago,

More information

arxiv:astro-ph/ v1 2 Mar 2001

arxiv:astro-ph/ v1 2 Mar 2001 Submillimeter CO emission from shock-heated gas in the L1157 outflow Naomi HIRANO Department of Astronomical Science, Graduate University for Advanced Studies, Mitaka, Tokyo, 181-8588, JAPAN arxiv:astro-ph/0103036v1

More information

DUST EMISSION FROM PROTOSTARS: THE DISK AND ENVELOPE OF HH 24 MMS

DUST EMISSION FROM PROTOSTARS: THE DISK AND ENVELOPE OF HH 24 MMS THE ASTROPHYSICAL JOURNAL, 449 : L139 L142, 1995 August 20 1995. The American Astronomical Society. All rights reserved. Printed in U.S.A. DUST EMISSION FROM PROTOSTARS: THE DISK AND ENVELOPE OF HH 24

More information

Mathematics 3 Curs /Q1 - First exam. 31/10/13 Grup M1 Lecturers: Núria Parés and Yolanda Vidal

Mathematics 3 Curs /Q1 - First exam. 31/10/13 Grup M1 Lecturers: Núria Parés and Yolanda Vidal Mathematics 3 Curs 013-014/Q1 - First exam. 31/10/13 Grup M1 Lecturers: Núria Parés and Yolanda Vidal Name: Calculator: [Generic Competency - 5% of the final grade of the subject a) Expresseu el nombre

More information

TESINA. Escola Tècnica Superior d Enginyers de Camins, Canals i Ports de Barcelona

TESINA. Escola Tècnica Superior d Enginyers de Camins, Canals i Ports de Barcelona TESINA Escola Tècnica Superior d Enginyers de Camins, Canals i Ports de Barcelona Títol: TRAFFIC STREAM MACRO AND MICRO ANALYSIS IN AP-7 TURNPIKE Autor SORIGUERA i FARRÉS, JORDI Tutor SORIGUERA i MARTÍ,

More information

High density molecular clumps around protostellar candidates

High density molecular clumps around protostellar candidates ASTRONOMY & ASTROPHYSICS APRIL II 1999, PAGE 333 SUPPLEMENT SERIES Astron. Astrophys. Suppl. Ser. 136, 333 361 (1999) High density molecular clumps around protostellar candidates R. Cesaroni, M. Felli,

More information

elevation in the Langtang Valley in Nepal, using Landsat remotely sensed data from

elevation in the Langtang Valley in Nepal, using Landsat remotely sensed data from PROJECTE O TESINA D ESPECIALITAT Títol Spatial and seasonal variability of the snowline elevation in the Langtang Valley in Nepal, using Landsat remotely sensed data from 1999-2003 Autor/a Marc Girona

More information

Structural Reliability Analysis and Robust Design of Offshore Wind Turbine Support Structures

Structural Reliability Analysis and Robust Design of Offshore Wind Turbine Support Structures Structural Reliability Analysis and Robust Design of Offshore Wind Turbine Support Structures Marc Garcia Llado Wind Energy Submission date: June 2015 Supervisor: Michael Muskulus, BAT Co-supervisor: Lars

More information

Non-Profit Academic Project, developed under the Open Acces Initiative

Non-Profit Academic Project, developed under the Open Acces Initiative Red de Revistas Científicas de América Latina, el Caribe, España y Portugal Sistema de Información Científica Armen. L. Gyulbudaghian, Jorge May, L. Gonzáles, R. A. Méndez Nebulous Objects in the Southern

More information

An interferometric study of the HH 288 molecular outflow

An interferometric study of the HH 288 molecular outflow A&A 375, 1018 1031 (2001) DOI: 10.1051/0004-6361:20010896 c ESO 2001 Astronomy & Astrophysics An interferometric study of the HH 288 molecular outflow F. Gueth 1,2, P. Schilke 1, and M. J. McCaughrean

More information

2 Motte & André: Density structure of protostellar envelopes is based on a relatively simple, semi-analytical similarity solution for the collapse (Sh

2 Motte & André: Density structure of protostellar envelopes is based on a relatively simple, semi-analytical similarity solution for the collapse (Sh A&A manuscript no. (will be inserted by hand later) Your thesaurus codes are: (08.05.1; 09.08.1) ASTRONOMY AND ASTROPHYSICS October 30, 2000 The circumstellar environment of low-mass protostars: A millimeter

More information

Progressive dispersal of the dense gas in the environment of early-type and late-type Herbig Ae-Be stars

Progressive dispersal of the dense gas in the environment of early-type and late-type Herbig Ae-Be stars Astron. Astrophys. 334, 253 263 (1998) Progressive dispersal of the dense gas in the environment of early-type and late-type Herbig Ae-Be stars A. Fuente 1, J. Martín-Pintado 1, R. Bachiller 1, R. Neri

More information

Màster en Enginyeria de Camins, Canals i Ports. Structural Reliability Analysis and Robust Design of Offshore Wind Turbine Support Structures

Màster en Enginyeria de Camins, Canals i Ports. Structural Reliability Analysis and Robust Design of Offshore Wind Turbine Support Structures TESI DE MÀSTER Màster Màster en Enginyeria de Camins, Canals i Ports Títol Structural Reliability Analysis and Robust Design of Offshore Wind Turbine Support Structures Autor Marc Garcia Lladó Tutor Prof.

More information

Microwave emissions, critical tools for probing massive star formation

Microwave emissions, critical tools for probing massive star formation Microwave emissions, critical tools for probing massive star formation Function of NH 3 molecule Yuefang Wu Astronomy Department Peking University Outline 1. Star formation regions and their probing Stars

More information

A MULTI-TRANSITION SEARCH FOR CLASS I METHANOL MASERS

A MULTI-TRANSITION SEARCH FOR CLASS I METHANOL MASERS A MULTI-TRANSITION SEARCH FOR CLASS I METHANOL MASERS Cara Denise Battersby MIT Haystack Observatory REU Summer 2004 Mentors: Preethi Pratap and Phil Shute ABSTRACT Class I methanol masers have been detected

More information

Fermilab FERMILAB-THESIS

Fermilab FERMILAB-THESIS Fermilab FERMILAB-THESIS-2002-01 Contents Resum Acknowledgements i i Introduction 1 1 Standard Model Higgs Boson Physics 5 1.1 The Standard Model........................... 5 1.1.1 Electromagnetic Interaction...................

More information

arxiv:astro-ph/ v1 15 Apr 2002

arxiv:astro-ph/ v1 15 Apr 2002 A&A manuscript no. (will be inserted by hand later) Your thesaurus codes are: 09(09.09.01 HH 2;09.01.1;09.03.1;09.03.13.2;08.06.02;13.19.3) ASTRONOMY AND ASTROPHYSICS The Molecular Condensations Ahead

More information

INITIAL CONDITIONS. Paola Caselli. School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES. Protoplanetary disks

INITIAL CONDITIONS. Paola Caselli. School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES. Protoplanetary disks Paola Caselli School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES Protoplanetary disks INITIAL CONDITIONS Boley 2009 Quiescent molecular clouds High-mass star forming regions Pre-stellar

More information

EMBEDDED YOUNG STELLAR POPULATION IN THE GALACTIC MOLECULAR CLOUD ASSOCIATED WITH IRAS

EMBEDDED YOUNG STELLAR POPULATION IN THE GALACTIC MOLECULAR CLOUD ASSOCIATED WITH IRAS RevMexAA (Serie de Conferencias), 37, 165 169 (2009) EMBEDDED YOUNG STELLAR POPULATION IN THE GALACTIC MOLECULAR CLOUD ASSOCIATED WITH IRAS 18236-1205 R. Retes, 1,2 A. Luna, 1 Y. D. Mayya, 1 and L. Carrasco

More information

Millimetre Science with the AT

Millimetre Science with the AT Millimetre Science with the AT Astrochemistry with mm-wave Arrays G.A. Blake, Caltech 29Nov 2001 mm-arrays: Important Features - Spatial Filtering - Transform to image plane - Cross Correlation (Sub)Millimeter

More information

Conferencia (o xerrada) : "Tectònica Global: La dinàmica d'un planeta actiu"

Conferencia (o xerrada) : Tectònica Global: La dinàmica d'un planeta actiu Conferencia (o xerrada) : "Tectònica Global: La dinàmica d'un planeta actiu" El progrés dels darrers anys de les tècniques de geofísica i d'adquisició de dades mitjançant satèl lits han revolucionat la

More information

CONFORMAL PREDICTION OF AIR POLLUTION CONCENTRATIONS FOR THE BARCELONA METROPOLITAN REGION

CONFORMAL PREDICTION OF AIR POLLUTION CONCENTRATIONS FOR THE BARCELONA METROPOLITAN REGION CONFORMAL PREDICTION OF AIR POLLUTION CONCENTRATIONS FOR THE BARCELONA METROPOLITAN REGION Olga IVINA Dipòsit legal: Gi. 473-2013 http://hdl.handle.net/10803/108341 Conformal prediction of air pollution

More information

DISTÀNCIES, LEVERAGE I OUTLIERS EN L ANÀLISI MULTIVARIANT

DISTÀNCIES, LEVERAGE I OUTLIERS EN L ANÀLISI MULTIVARIANT DISTÀNCIES, LEVERAGE I OUTLIERS EN L ANÀLISI MULTIVARIANT Anàlisi Multivariant, UPF, Tardor del 2012 1 Distància d ts entre dos punts, matriu D de distàncies 2 Distància entre punts distancia entre dos

More information

ISO-LWS two-colour diagram of young stellar objects

ISO-LWS two-colour diagram of young stellar objects Mon. Not. R. Astron. Soc. 330, 1034 1040 (2002) ISO-LWS two-colour diagram of young stellar objects S. Pezzuto, 1P F. Grillo, 1 M. Benedettini, 1 E. Caux, 2 A. M. Di Giorgio, 1 T. Giannini, 3 S. J. Leeks,

More information

Deflection of a Protostellar Outflow: The Bent Story of NGC 1333 IRAS 4A. NGC 1333 Cluster Forming Region. Driving Source. IRAS 4A Protobinary System

Deflection of a Protostellar Outflow: The Bent Story of NGC 1333 IRAS 4A. NGC 1333 Cluster Forming Region. Driving Source. IRAS 4A Protobinary System Deflection of a Protostellar Outflow: The Bent Story of NGC 1333 IRAS 4A SNU Colloquium 2006. 3. 22. Minho Choi Evolutionary Scenario of Low-Mass Young Stellar Objects Classification Spectral Energy Distribution

More information

arxiv: v1 [astro-ph] 27 Sep 2008

arxiv: v1 [astro-ph] 27 Sep 2008 Handbook of Star Forming Regions Vol. I Astronomical Society of the Pacific, 2008 Bo Reipurth, ed. Star Forming Regions in Cepheus arxiv:0809.4761v1 [astro-ph] 27 Sep 2008 Mária Kun Konkoly Observatory,

More information

arxiv:astro-ph/ v1 30 Jun 1999

arxiv:astro-ph/ v1 30 Jun 1999 VLA Observations of H 2 O Masers in the Class 0 Protostar S106 FIR: Evidence for a 10 AU-Scale Accelerating Jet-like Flow Ray S. FURUYA arxiv:astro-ph/9906495v1 30 Jun 1999 Department of Astronomical Science,

More information

Lecture 19 CO Observations of Molecular Clouds

Lecture 19 CO Observations of Molecular Clouds Lecture 9 CO Observations of Molecular Clouds. CO Surveys 2. Nearby molecular clouds 3. Antenna temperature and radiative transfer 4. Determining cloud conditions from CO References Tielens, Ch. 0 Myers,

More information

Computation of Normally Hyperbolic Invariant Manifolds

Computation of Normally Hyperbolic Invariant Manifolds Computation of Normally Hyperbolic Invariant Manifolds Marta Canadell Cano Aquesta tesi doctoral està subjecta a la llicència Reconeixement 3.. Espanya de Creative Commons. Esta tesis doctoral está sujeta

More information

WATER MASERS IN THE CIRCUMSTELLAR ENVIRONMENTS OF YOUNG STELLAR OBJECTS

WATER MASERS IN THE CIRCUMSTELLAR ENVIRONMENTS OF YOUNG STELLAR OBJECTS THE ASTRONOMICAL JOURNAL, 115:1599È1609, 1998 April ( 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A. WATER MASERS IN THE CIRCUMSTELLAR ENVIRONMENTS OF YOUNG STELLAR OBJECTS

More information

The Molecular Condensations Ahead of Herbig-Haro Objects. I Multi-transition Observations of HH 2

The Molecular Condensations Ahead of Herbig-Haro Objects. I Multi-transition Observations of HH 2 A&A manuscript no. (will be inserted by hand later) Your thesaurus codes are: 09(09.09.01 HH 2;09.01.1;09.03.1;09.03.13.2;08.06.02;13.19.3) ASTRONOMY AND ASTROPHYSICS April 16, 2002 The Molecular Condensations

More information

1. INTRODUCTION 2. OBSERVATIONS 3. RESULTS AND DISCUSSION

1. INTRODUCTION 2. OBSERVATIONS 3. RESULTS AND DISCUSSION THE ASTROPHYSICAL JOURNAL, 531:861È867, 2000 March 10 ( 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A. A CLUSTER OF RADIO SOURCES NEAR GGD 14 Y. GO MEZ AND L. F. RODRI

More information

Aspectes Clàssics i Quàntics de Forats Negres en Diverses Dimensions

Aspectes Clàssics i Quàntics de Forats Negres en Diverses Dimensions Doctorat de Física Avançada Bienni 2003-2005 Aspectes Clàssics i Quàntics de Forats Negres en Diverses Dimensions Pau Figueras i Barnera Departament de Física Fonamental Grup de Cosmologia i Gravitació

More information

arxiv: v1 [astro-ph] 6 Aug 2007

arxiv: v1 [astro-ph] 6 Aug 2007 Multiple Sources toward the High-mass Young Star S140 IRS 1 Miguel A. Trinidad 1 José M. Torrelles 2, Luis F. Rodríguez 3, Salvador Curiel 4 trinidad@astro.ugto.mx arxiv:0708.0820v1 [astro-ph] 6 Aug 2007

More information

The Role and Usage of Libration Point Orbits in the Earth Moon System

The Role and Usage of Libration Point Orbits in the Earth Moon System The Role and Usage of Libration Point Orbits in the Earth Moon System Elisa Maria Alessi ADVERTIMENT. La consulta d aquesta tesi queda condicionada a l acceptació de les següents condicions d'ús: La difusió

More information

Treball Final de Grau

Treball Final de Grau Tutor Dr. Joaquín F. Pérez de Benito Departament de Ciència de Materials i Química Física Treball Final de Grau Kinetic study of the complexation of chromium(iii) by L-glutamic acid Estudi cinètic de la

More information

ASTRONOMY AND ASTROPHYSICS. An investigation of the B335 region through far infrared spectroscopy with ISO

ASTRONOMY AND ASTROPHYSICS. An investigation of the B335 region through far infrared spectroscopy with ISO Astron. Astrophys. 343, 266 272 (1999) An investigation of the B335 region through far infrared spectroscopy with ISO ASTRONOMY AND ASTROPHYSICS B. Nisini 1, M. Benedettini 1, T. Giannini 1,2,3, P.E. Clegg

More information

A note on inertial motion

A note on inertial motion Atmósfera (24) 183-19 A note on inertial motion A. WIIN-NIELSEN The Collstrop Foundation, H. C. Andersens Blvd. 37, 5th, DK 1553, Copenhagen V, Denmark Received January 13, 23; accepted January 1, 24 RESUMEN

More information

within entire molecular cloud complexes

within entire molecular cloud complexes The earliest phases of high-mass stars within entire molecular cloud complexes Frédérique Motte (CEA-Saclay, AIM) Collaborators: S. Bontemps (Obs Bordeaux), N. Schneider, J. Grac (CEA-Saclay), P. Schilke,

More information

Protostellar Jets in the ngvla Era

Protostellar Jets in the ngvla Era Protostellar Jets in the ngvla Era Luis F. Rodríguez (IRyA- UNAM, Mexico) In collabora@on with G. Anglada, C. Carrasco- González, L. Zapata, A. Palau, R. Galván- Madrid, C. Rodríguez- Kamenetzky, A. Araudo,

More information

A Search for NH 3. D Bonn, Germany 2 Australia Telescope National Facility, CSIRO, PO Box 76,

A Search for NH 3. D Bonn, Germany 2 Australia Telescope National Facility, CSIRO, PO Box 76, Publ. Astron. Soc. Aust., 1997, 14, 246 50. A Search for NH 3 Magellanic in the Large Cloud Jürgen Osterberg 1, Lister Staveley-Smith 2, Joel M. Weisberg 3, John M. Dickey 4 and Ulrich Mebold 1 1 Radioastronomisches

More information

Payne-Scott workshop on Hyper Compact HII regions Sydney, September 8, 2010

Payne-Scott workshop on Hyper Compact HII regions Sydney, September 8, 2010 Payne-Scott workshop on Hyper Compact HII regions Sydney, September 8, 2010 Aim Review the characteristics of regions of ionized gas within young massive star forming regions. Will focus the discussion

More information

MOLECULAR LINES IN BOK GLOBULES AND AROUND HERBIG Ae/Be STARS

MOLECULAR LINES IN BOK GLOBULES AND AROUND HERBIG Ae/Be STARS MOLECULAR LINES IN BOK GLOBULES AND AROUND HERBIG Ae/Be STARS arxiv:astro-ph/9311016v1 5 Nov 1993 F. Scappini 1, G.G.C. Palumbo 2, G. Bruni 1, and P. Bergman 3 1 Istituto di Spettroscopia Molecolare, C.N.R.,

More information

Mid-infrared images of compact and ultracompact HII regions: W51 and W75N.

Mid-infrared images of compact and ultracompact HII regions: W51 and W75N. Mem. S.A.It. Vol. 74, 146 c SAIt 2003 Memorie della Mid-infrared images of compact and ultracompact HII regions: W51 and W75N. Paolo Persi 1, Anna Rosa Marenzi 1, Maurcio Tapia 2 and Joaquín Bohigas 2,

More information

arxiv: v1 [astro-ph.ga] 20 Jul 2011

arxiv: v1 [astro-ph.ga] 20 Jul 2011 To appear in the PASJ Radio Imaging of the NGC 1333 IRAS 4A Region: Envelope, Disks, and Outflows of a Protostellar Binary System arxiv:1107.3877v1 [astro-ph.ga] 20 Jul 2011 Minho CHOI 1,2, Miju KANG 1,

More information

A.1 The fountains of youth: irradiated break-out of outflows in S140

A.1 The fountains of youth: irradiated break-out of outflows in S140 Appendix A Published Papers A.1 The fountains of youth: irradiated break-out of outflows in S140 John Bally, Bo Reipurth, Josh Walawender and Tina Armond The Astronomical Journal, 124: 2152 2163, 2002

More information

Dynamic force spectroscopy and folding kinetics in molecular systems

Dynamic force spectroscopy and folding kinetics in molecular systems Dynamic force spectroscopy and folding kinetics in molecular systems Anna Alemany i Arias ADVERTIMENT. La consulta d aquesta tesi queda condicionada a l acceptació de les següents condicions d'ús: La difusió

More information

INTERFEROMETRIC MASER OBSERVATIONS FROM OUTFLOWS/DISKS IN STAR-FORMING REGIONS

INTERFEROMETRIC MASER OBSERVATIONS FROM OUTFLOWS/DISKS IN STAR-FORMING REGIONS RevMexAA (Serie de Conferencias), 13, 108 113 (2002) INTERFEROMETRIC MASER OBSERVATIONS FROM OUTFLOWS/DISKS IN STAR-FORMING REGIONS José M. Torrelles, 1 Nimesh A. Patel, 2 José F. Gómez, 3 and Guillem

More information

Extended Near-Infrared Emission from Candidate Protostars in the Taurus-Auriga Molecular Cloud

Extended Near-Infrared Emission from Candidate Protostars in the Taurus-Auriga Molecular Cloud Extended Near-Infrared Emission from Candidate Protostars in the Taurus-Auriga Molecular Cloud Shinae Park Physics Department, University of California, 366 LeConte Hall, Berkeley, CA 9472-73 and Scott

More information

arxiv:astro-ph/ v1 10 Feb 2005

arxiv:astro-ph/ v1 10 Feb 2005 arxiv:astro-ph/0502214v1 10 Feb 2005 PRECURSORS OF UCHII REGIONS & THE EVOLUTION OF MASSIVE OUTFLOWS Henrik Beuther Harvard-Smithsonian Center for Astrophysics 60 Garden Street Cambridge, MA 02138 USA

More information

Probing the embedded phase of star formation with JWST spectroscopy

Probing the embedded phase of star formation with JWST spectroscopy Probing the embedded phase of star formation with JWST spectroscopy NIRSPEC Spitzer NGC 1333 Low mass Herschel Cygnus X High mass Jorgensen et al. Gutermuth et al. 10 10 Motte, Henneman et al. E.F. van

More information

INDEX OF SUBJECTS 6, 14, 23, 50, 95, 191 4, 191, 234

INDEX OF SUBJECTS 6, 14, 23, 50, 95, 191 4, 191, 234 INDEX OF SUBJECTS Abundances, elemental Abundances, ionic AGB stars (see Stars, AGB) Age, nebulae Asymptotic Giant Branch (AGB) Be stars (see Stars, Be) Bipolar structure, nebulae Carbon stars Carbon stars,

More information

Explicit Bound states and Resonance fields in Effective Field Theories

Explicit Bound states and Resonance fields in Effective Field Theories Explicit Bound states and Resonance fields in Effective Field Theories Jaume Tarrús Castellà Aquesta tesi doctoral està subjecta a la llicència Reconeixement- NoComercial 3.0. Espanya de Creative Commons.

More information

STARLESS CORES. Mario Tafalla. (Observatorio Astronómico Nacional, Spain)

STARLESS CORES. Mario Tafalla. (Observatorio Astronómico Nacional, Spain) STARLESS CORES Mario Tafalla (Observatorio Astronómico Nacional, Spain) Outline: 1. Internal Structure a. Introduction b. How to characterize the internal strcuture of starless cores c. L1498 & L1517B:

More information

Exploring the Evolution of Dark Energy and its Equation of State

Exploring the Evolution of Dark Energy and its Equation of State Exploring the Evolution of Dark Energy and its Equation of State Advisor: Dra. Pilar Ruiz-Lapuente Universitat de Barcelona 12th February, 2008 Overview 1 Motivació 2 Introduction 3 Evolving Cosmological

More information

STUDY ON STORAGE ENERGY DEVICES: SUPERCAPACITORS, A GREEN ALTERNATIVE

STUDY ON STORAGE ENERGY DEVICES: SUPERCAPACITORS, A GREEN ALTERNATIVE STUDY ON STORAGE ENERGY DEVICES: SUPERCAPACITORS, A GREEN ALTERNATIVE TITLE: Study on storage energy devices: supercapacitors, a green alternative MASTER DEGREE: Master in Science in Telecommunication

More information

Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068 Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068 Dan Evans (MIT Kavli Institute), Patrick Ogle (Caltech), Herman Marshall (MIT), Mike Nowak (MIT), Kim Weaver (GSFC),

More information

Lecture 26 Clouds, Clumps and Cores. Review of Molecular Clouds

Lecture 26 Clouds, Clumps and Cores. Review of Molecular Clouds Lecture 26 Clouds, Clumps and Cores 1. Review of Dense Gas Observations 2. Atomic Hydrogen and GMCs 3. Formation of Molecular Clouds 4. Internal Structure 5. Observing Cores 6. Preliminary Comments on

More information

MOLECULAR COUNTERPARTS OF ULTRACOMPACT H ii REGIONS WITH EXTENDED ENVELOPES Kee-Tae Kim 1,2 and Bon-Chul Koo 2

MOLECULAR COUNTERPARTS OF ULTRACOMPACT H ii REGIONS WITH EXTENDED ENVELOPES Kee-Tae Kim 1,2 and Bon-Chul Koo 2 The Astrophysical Journal, 596:362 382, 23 October 1 # 23. The American Astronomical Society. All rights reserved. Printed in U.S.A. MOLECULAR COUNTERPARTS OF ULTRACOMPACT H ii REGIONS WITH EXTENDED ENVELOPES

More information

H II and hot dust emission around young massive stars in G

H II and hot dust emission around young massive stars in G Astron. Astrophys. 329, 233 242 (1998) ASTRONOMY AND ASTROPHYSICS H II and hot dust emission around young massive stars in G9.62+0.19 Leonardo Testi 1,2, Marcello Felli 3, Paolo Persi 4, and Miguel Roth

More information

arxiv:astro-ph/ v1 20 Nov 2003

arxiv:astro-ph/ v1 20 Nov 2003 Astronomy & Astrophysics manuscript no. ngc2316 June 11, 2018 (DOI: will be inserted by hand later) Near infrared imaging of NGC 2316 P. S. Teixeira 1, S. R. Fernandes 1, J. F. Alves 2, J. C. Correia 1,

More information

Treball Final de Grau

Treball Final de Grau Tutors Dr. Héctor Bagán Navarro Department of Chemical Engineering and Analytical Chemistry Dr. Álex Tarancón Sanz Department of Chemical Engineering and Analytical Chemistry Treball Final de Grau Development

More information

L INTRODUCTION. The Astrophysical Journal, 598:L115 L119, 2003 December 1

L INTRODUCTION. The Astrophysical Journal, 598:L115 L119, 2003 December 1 The Astrophysical Journal, 598:L115 L119, 2003 December 1 2003. The American Astronomical Society. All rights reserved. Printed in U.S.A. EVIDENCE FOR EVOLUTION OF THE OUTFLOW COLLIMATION IN VERY YOUNG

More information